T-1200 vs T-800 pumps

I'm starting to build my semi automated system and can't decide which one's to go with. I would like the speed of the 1200's but it seems like alot of dinking around with the odd 1 1/8" size. I know the 800's screw right in to Fly High Sacs and it sounds really simple to just do it that way. I think it would also be another $200 in part if I used the 1200's. What are the fill times on a 750 sac? Would it be safe to say if a 1200 would fill it in 6 minutes the 800 would do it in 9 minutes? I may have just answered my own question but would like to hear from someone with experience. Also I havn't really seen a good way to put in a accuated valve right after the scoop. I would like one valve in my system to shut off all water coming in, I plan to come thru the hull with an 1 1/2" scoop.