it basically comes down to personal preference and how legal you want the car to be.
I prefer the rotary (obviously) because of the way they rev, light weight and compact design.
The SR20 is an excellent engine with a world of aftermarket support, but in the end both are going to cost $$$ to modify and maintain, most people will say the rotary needs more maintain but IMO it needs no more than whats needed on any other car. I do a service on all my cars after 5000k's, as for rebuilds like any other engine if looked after it should last just as long.
I had an old 12A stocker in a S2 that had over 200 000Ks on it and was still going strong, couldnt kill it even when we tried (was upgrading to a ported 13B). reved off the clock bone cold, reved past 9 grand for over 2mins on many occasions and overheated several times and it still went strong and hard!