You aren't the only one; I've noticed this too. Not only do I feel the 5 min puzzles are a tougher pool than the 3 min puzzles, but Puzzle Rush Survival seems even tougher than 3 min and 5 min. I am virtually certain I've seen certain puzzles in different rushes (so some puzzles must share the pool), but I sense that the longer time puzzle rush (survival untimed being the longest) also includes a series of tougher puzzles mixed in there as well.
Puzzle Rush discrepancy 5 min v 3 min
You aren't the only one; I've noticed this too. Not only do I feel the 5 min puzzles are a tougher pool than the 3 min puzzles, but Puzzle Rush Survival seems even tougher than 3 min and 5 min. I am virtually certain I've seen certain puzzles in different rushes (so some puzzles must share the pool), but I sense that the longer time puzzle rush (survival untimed being the longest) also includes a series of tougher puzzles mixed in there as well.
Glad to hear I'm not the only one, thanks. Can't say I do survival very often but it wouldn't surprise me if it's a different pool there too. I find it kinda frustrating and end up doing 3 min almost exclusively :/

Makes sense. When I started doing puzzle rush on chess.com years ago, 5 min was the ONLY puzzle rush available. Since then, chess.com has added 3 min and survival. It took a little getting used to, but I usually just stayed with 5 min. It was only months after that which I began trying 3 min and survival. I will also note that I used to have a free membership back then, so I would only get one 5 min puzzle rush attempt per day.
I took a long break from puzzle rush and then I got motivated to aim for a very ambitious goal of 50+ survival score. It took me about one full year of trying, but I eventually reached that goal:
https://www.chess.com/blog/KeSetoKaiba/puzzle-rush-survival-50-goal-reached
and now I've even gone a little further than this (even though I haven't tried Survival in a while).
Congrats on 50+, it's a great score! Honestly I'd forgotten they began with only the 5 minute version, I may have been a bit less active back then. I go through periods of inactivity with chess but in general I've been using the site since 2013 (different account to begin with) or so, mostly for tactics
Am I crazy or are the individual puzzles in 5 min rush harder than those you get in 3 min with the same rating? Obviously the puzzles all have ratings and you get puzzles rated the same, but puzzle ratings in my experience are inconsistent/unreliable in predicting difficulty. Your average 1500 puzzle in 5 min seems harder than a 1500 in 3 min.
Could it be that the pool of puzzles used for 5 min rush have longer solve times on average than those for 3 min? Maybe I'm just crazy but it's felt like this to me since puzzle rush was introduced.