I have used both.
The PE90 is nice for precision work in a semi platform, the swiss are all about the accuracy. Real downside to the PE90s is the forward weight, its not a fast run'n gun type rifle. great for range work and Gophers. The mid length ones are much nicer to use as they are lighter and faster to point, downside is 17.9" barrel.
The Tavor is nice for balance and speed, certainly one of the nicer bullpups out there. It has the military "liability trigger" that you would expect from a gun designed for use by soldiers working primarily in built up areas close to civilian populations. The trigger can be fixed though... Some say its not as accurate but I think there are so few in Canada that few people have worked out just what ammo and optics etc these like.
If you can, buy both. I like the Tavor cause its faster, lighter and suits the type of shooting I do. The PE90 is a close second though, they are really nice rifles. Looking online today and the Sig556 is on sale for $999.00USD down south.