Yes, in some ways I prefer the rangefinder format and smaller body of the GX1 as long as it has a decent grip - but the grip on the G3 and GX1 could both be improved (compared to say the Nex grip which is better, or the G5 grip which is also an improvement on the G3). But I also prefer an evf and the add on one is a) too expensive and b) bulky/awkward (taking the camera in and out of a bag etc) and I would be worried about damaging it.
This side by sidecomparison is quite useful:
http://www.ephotozine.com/article/panasonic-lumix-dmc-gx1-vs-dmc-g3-review-18312
As you say -it's good that Panasonic offer both options unlike Olympus who so far only offer a built in evf in one camera (OMD) and that's a lot more expensive than the G3! There are rumours of a GX2 with a built in evf and of an Olympus Pen with a built in evf too - to compete with the Nex 6 I guess, but no idea how much truth (if any) there is in the rumours.