They're both amazing, but if I had to choose, Spyro. Crash can REALLY get under your skin very quickly, but it is fun once you get the hang of it. Maybe it's just because I haven't put enough time into it.
But Spyro, my gosh. It's hard, but it's easy. I have 100%+ (because there is extra stuff, like getting all the skill points) all 3 games on PSOne and the re-release. The first one took me 6 years to beat to completion, and I think I did Ripto's Rage way faster. Upon re-release, it took me a week to complete all 3, mainly because I remembered everything from play hundreds of times over.
The music is fun, the enemies are hilarious, the stories are actually good. You get to switch characters in Year of the Dragon, depending on world. The power-ups are such a relief to have, and actually make you want to play through a second time. There are numerous cheat codes to help you out as well, if you ever feel a bit stuck. I'm sure Crash has them as well, but I have never looked.
In the second one (Ripto's), I would say it's a bit more challenging, but in a good way. You may want to throw your controller across the room for some of the quests, but what is a game if you don't get angry at it. Personally my favourite, as I loved the worlds overall. Even the water ones were okay, and I know a lot of people that hate water areas (Mario, Zelda, etc.)
If you have an opportunity to try either, I would say start with Crash. Reason why is because once you play Spyro, you won't want to play Crash (or that could just be me )
Either way, hope you have fun! They are both great games