I say the Prelude because it handles much better, the h22a4 is a very good engine to built from. The Full double wishbone suspension is basically the best type of suspension out there and that's why they use it on most race cars and exotics - the Prelude has this type of suspension, not even the RSX-S or 04+ Civic Si have it. Dc2 integras, S2000's, NSX's have it though because they give an awesome ride while giving exceptional handling and stability. This is probably the strongest atribute of Prelude's.
The G20's suspension has a modified 3-link wishbone suspension which is like a double wishbone suspension, but not quite. They do this to keep costs down and also to keep it a little better ride quality while giving very good handling, but even though this is a good alternative, it's still a pseudo double wishbone.
The rear suspension is a twist beam like the pre-6th generation maximas and altimas. It's basically a solid beam suspension but it's not solid, it is cut and held on by a section which twists durring suspension changes so it acts like a fully independent suspension all while keeping the simplicity and lowering the costs of manufacturing.
I have a 3rd generation Prelude and a 4th gen Maxima and I can tell the difference in handling and ride quality and the Maxima (pretty much the same suspension as the G20, but modified to fit). The Maxima's rear likes to hop around and it can really get scary when you have to navigate through a turn over bumps. The prelude handles smoothly and it makes you feel comfortable going very fast around corners - it will make you feel and seem like a professional driver, it's an awesome car to impress friends with in the curves.
Suspensions aside, the g20 has the 2.0L DOHC Sr20de which can be swapped out for a pulsar (or any awd sr20det to use with fwd transaxle) sr20det (or sr20ve) engine, this can make it smoke the Prelude with it's H22a4 (200hp). It's a good car, but obviously not my choice vs the two...I think the Prelude looks nicer, sleeker, but not as luxury-sport looking as the G20 is.
It's basically, if you want to keep your car stock, I say Prelude, if you want to modify then they should tie, then it boils down to luxury and 4 doors vs 2 doors.....Your Choice.