The pool wall simply sits in the track, one isn't harder than the other. If anything resin is easier as the bottom rails simply snap into the legs and don't need to be screwed in.
There's people out there that contend that resin is inferior - it's not. I have a resin pool and the set up was great, it can endure a hard Canadian winter, won't rust and the parts are very strong.
Resin pools are a great option if the added expense is within budget, I would highly recommend the upgrade, but if it's not in budget get what you can afford and have fun!