I have never sailed without battens in the jib, but I think you will find that the leach will flutter pretty badly in any kind of breeze. I think the jibs have alittle bit of positive roach cut into them so if it is unsupported, they will probably want to curl or flutter. I think one of the other guys on this forum has sailed without the battens in the jib, maybe he can chime in... As far as shape goes, the furler jib has alittle more shape in the front while the battened jib is a little bit flatter (atleast that is how mine look). I like the furler jib for light air and the battened one for everything else. Alot of the battened I20 jibs I've seen have very little shape in the top of the sail (not that you can put much shape in up there), certainly less than the furling jib.
I'm guessing you want to furl a jib that has the horizontal battens in it?? This also depends on if you are racing or not?? I think it would definitely be slower and probably will not help the life of your jib if you do not have the battens. something else you could consider is having a local sailmaker put vertical battens into your jib. Probably wouldn't cost too much and will get you the same end result.
cheers..