My experience with bullpups are limited. I've only shot the Steyr AUG, FS2000, Tavor and the P90. For me, it would be a toss up between the FS2000 and the Tavor, but my vote went to the FS2000 for being suitable for ambi use. Yes, the Tavor can be configured to eject either side and a left "can" shoot a Tavor configured for a right side eject, but it's enough that it would be a significant nuisance to many shooters. The Tavor is on the heavy side, but I think it's a solid gun.
Not sure, but IIRC the FS2000 only like USGI mags. I've shot the Tavor with Troy polymer mags, but not PMags.