Well, generally, you have to decide on what you're gonna make the story be about. If it's gonna be an extremely romantic story, don't go for 4-panels, you'll limit yourself too much. In that case, it would obviously have to be a shoujo with the very vague panel divides.
If it's mainly a commedy and romance is just a backdrop, then use the 4-panels by all means, but keep in mind that you can't develop a plot very well with 4-panels (which are called yonkoma, btw) and you'll have to be able to come up with a gag line for each and every yonkoma you write.
Then, maybe it's a romance, but you want to make it a romance geared more towards a sort of neither particularly male nor female audience. In that case, you'd want to go for a more shonen look to the panels. Mainly it's a bad idea to use shonen-style panels unless you're going to have a lot of action, cuz otherwise they end up being too uniform-looking. You could also do a style of paneling that's not really shonen or shoujo. The best example I can think of this is Kiyohiko Azuma's "Yotsuba&!" which you can find here: www.koiwai.biz.
Or maybe I'm just rambling on pointlessly because you don't want it to be manga-style at all, but I assumed you did cuz you mentioned yonkoma, but just shut me up now if you didn't.
"Fools and scisors can both be sharp when handled right."
- Hiei, Yuu Yuu Hakusho
2006 - Already Been Dead = WIN!
2007 - Punctuation = Epic Fail....
2008 - ......
2009 - Super Bad Smash = |