Personally, the positive that would sway me to a laser over the F5, is the ability to 1D race it. The slightly less room for two folks not withstanding. In Jr high I took a class on some of the original hull #'s in the upper hundreds, and sailed with 2 of us onboard, it was not that bad! Then again the passenger in my case was curvacious cute!
Either in the end would be fine. Another to add, finding replacement parts etc is easier with a laser than an F5. Yes there will be performance differences, but in the end, really not enough to say that one is better overall to me for just going out and daysailing for fun. You will have fun with either! Both will serve what I believe you wanting in a boat.
She drives me boat,
I drives me dinghy!