Lots of differences. I have a 34j and did look at the Ace. I didn't like the smaller windshield. Also by the time you add the second ac unit a must have in Florida it's about the same price. With the 34j you get more bang for your buck with an outdoor kitchen, auto generator start a care free awning. Plus a much bigger motor home.
I own the 34J and have a friend with the Ace 30.2. I don't have much to add beyond what has already been said. But it really does depend on you. We have 5 kids and need the extra space. But we are certainly envious of them when they are able to leave the campsite and drive into Yosemite Valley. Something we wouldn't dream of doing with our 34J. But when it is rainy outside, they become envious of us. If you really feel like you need the extra space, go with the hurricane and use a toad. If you don't need to space, go with the Ace and leave the toad at home. Or if you are going to have longer stays, I would also go with the Hurricane. If you are only planning on short weekend trips, I would suggest the ACE. Gas mileage is also significantly different. He get 13.5 and I get about 11 mpg.
I have an Ace and I would love to know how your friend gets 13 mpg. I have never got above 8 mpg.