Stardust Crusaders (2014) is Jojo's Bizarre Adventure : the Animation (2012)'s sequel. But if you think about it seriously, there are a thousand things that are different between the two seasons, and which make undoubtedly SEASON 1 > SEASON 2. To some extent, you could speak of a DIFFERENT anime. I took a quick look on the reviews of other websites a moment ago : senscritique (barely), anidb (clearly) & anime news network (surely) all agree with me on which season is better, only douban doesn't and that can be explained easily : the community of douban does not understand SHIT to anime. All hail anidb !
Since I consider Jojo's Bizarre Adventure the Animation (2012 = season 1) as the best shounen anime of all time, this review is mostly going to be a comparison between the two, a comparison between the Master and the student.
Characters : Stardust Crusaders' has the worst Jojo so far. His look is definitely GAR, but the "R" in here is getting too much closer to an "Y". The chain on his neck, the hat on his head and that stupid cape make his design far less enjoyable than the two first ones. Personality wise, he is an empty shell, and this hurts even more since they had 24 episodes to develop him, whereas they had far less for the two previous Jojo's who had to share out the 24 episodes. When the two first Jojo's had a few first episodes to lay down some background (usually without much fights or as an appetizer) and stories in order to introduce the protagonists, their values & skills (honesty & raw force for the first, naughtiness & smartness for the second), this one only gets the bare minumum. The end result is that there will be no empathy for the character during the whole show. This 3rd Jojo's has almost no dialogue lines : he looks cold, avoids to talk, does the job (i.e. the killing) when necessary and contains all his emotions. The "Yare yare" (Good grief) that he keeps on repeating in every circumstance is DEFINITELY not cool... This goes to the extent that we might at some point doubt who is the main character... since this one does not get so much attention when the stories unfolds, & the creator focuses more on the other characters. This is also a big difference with the first season, in which one Jojo's is the boss & the others are only there in a support (Zeppeli the teacher) / secondary (Zeppeli the descendant) / commentary (Speedwagon) role and usually end up dying or beat up. In Stardust Crusaders, there are actually TWO Jojo's simultaneously. One plays the role of the Dark Powerful Silent Protagonist and the second of the Experienced Funny Talkative "secondary" character. + 3 other characters that actually get a lot of attention and a bit of development (especially Polnareff) : Avdol (the Wise & Temperate guy) whose Stand skills are Power & Fire, Kakyoin (Common Sense & Stabilising member of the group) whose Stand skills are Flexibility & Variety, Polnareff (the Silly & Funny guy with whom the viewer will often adopt the subjective point of view : i.e. Avdol's death) and whose Stand skills are Precision & Velocity. Of course the characters are created so that there is an Equilibrium & Complementarity in the group, and so that no one is powerful enough for overtaking the Protagonist's role. Classicaly, who will face the new bad guy depends on the powers that they each have, and on how powerful is the enemy. Sometimes they will face altogether some enemies which is pretty cool in terms of interaction and symbiosis.
Development (structure & fights) : Far less epic than Stardust Crusaders for many reasons. One of them is that there are too many enemies (representing for some weird reasons a card in the Tarot game, which is not adding anything to the show - except perhaps selling the fucking cards later ?). On average, each new enemy has a two-episodes span life, including half an episode of silly jokes and progress in the map, a cool or stealth entrance, the fight lasting 1 episode with a couple of predictable twists and then a conclusion with everyone being happy and teaching the bad guy a good lesson. It's almost a pokemon-like structure... The worst is that Dio never appears in any fight... He is far away "waiting" for the characters in the darkness, raping bitches and looking strong & cool with the Jojo's family star on his back. This again reminds a lot of the old european cartoons of the 90's, in which the main antagonist keeps sending small fries without moving his ass, while he's posing and showing his best evil laughter. The show is structured in a way that we know at each episode that the bad guy is going to get his ass kicked and that a new one is coming next and so on... If the characters were not road tripping from Japan to Egypt and if we didn't know that opponents are limited in number (Dio will necessarily run out of those FUCKING Tarot cards), the anime would have been simply BORING. Hopefully the road trip enables to see different settings and is helping for building the jokes (toilets in India, 讨价还价 in Arab countries, rigorous rules in Singapore etc...). It goes without saying that the MYSTERY of season 1 (related to the Mask, to the ancient cultures evil forces etc.) is completely absent. In the first season, the stakes were generally much higher : badass & super dangerous enemies (including Dio and the mask's embodiments) with some depth & backstory would show up and give a real hard time for the protagonists (causing heavy injuries, deaths and big emotional fuss). In Stardust Crusaders, everything is too easy and taken lightly. Except once, all superficial injuries disappear at the end of the fight and, opponents come one by one and end up begging for their lives without any dignity. And that leads us to one of the main points of this review : if you think about it in another way, one could argue that Jojo's is less of a shounen with serious fights than a funny comedy with loads of gag (adding the traveling adventure aspect, and it starts having a couple of common points with One Piece). This is not necessarily a critique, since the show is REALLY super funny, but mechanically less Epic and thrilling.
Other aspects : Aesthetically speaking, IMHO the first season's added effects were clearly better and engaging. They would for important moments, freeze the picture for a "cool phase" and add layers of colors and geometric forms all around in order to emphasize a situation and making it classy, usually during fights. This technique has sadly almost been abandoned in this anime... I thought it was brilliant in the first season. In the same spirit, moments when the colors of a given setting would start to beautifully distort and change are also less common in the sequel. The sceneries depicted were also more elaborate and beautiful in the latter. Otherwise the animation of this sequel is really well-made, even though the artistic value is a bit inferior to the predecessor. The music (including OP and especially the masterpiece song for the ending) is not as good as season 1 but still fits what's happening in the screen overall. The references to the rock n' roll & heavy metal world are also very rare compared to the first season, since the creators focused their references into general knowledge (geography, cultural aspects and bit of history) while describing the place where the characters stopped during their road trip.
Wish they do a sequel with more epicness, and with DIO !!!!!!! for God's sake.