Najo said:
My guess is they won't like gurps either btw. It uses 3d6 to test, its options are all over the place and there is no predetermined setting at all, it is all up to you to paint the canvas and choose what you want to go with it from the rules. Your players sound like they will hate you for it.
I also have a feeling that a group of strictly d20 lovers won't be an easy sell for GURPS. But still, they might surprise you.
On the setting thing though... while it's true that there is no set background in the core rules, that's what the supplements are for. If you go with 3E, pick up
GURPS Fantasy, which is pretty much the same as the 4E
Banestorm, as previously mentioned. Note that the 4E book entitled
Fantasy is *not* the same. That one is a cookbook of all kinds of fantasy options to build your own world from.
Some of the things off the top of my head that changed between 3E and 4E:
Passive Defense is gone (this was sort of like AC in D&D - the chance that your armor deflects a blow completely and added to your Defense roll. Now it's just a flat +3 for all Defense rolls.)
Point costs for DEX and INT are higher than STR and HT.
Point costs to advance in skills have been juggled a bit. Compare your 3E books to the GURPS Lite doc.
I can't remember if there's a whole lot different about Magic except for the general changes to skill costs. Psionic powers, however, have really been revamped to make them a lot more flexible to define specific abilities and their limitations.
One other difference is a design philosophy in 4E that no new rules will be introduced in supplemental books. Everything is in the core rules. Not to say the supplements aren't crunchy - they are, very much so. They simply show how to build off of the existing rules to get the options you want (and possibly eliminate a lot of GM/player arguments about point costs of limitations of abilities and the like by giving spelled-out examples. GURPS Powers is chock full of these.)