Isn't one of the major tenants of SL5x5 that getting sore and getting pumped have little to do with getting stronger? I may be wording it wrong but I got the impression several times while reading the e-book from the strong lifts site. I am not trying to convince you to drink the cool-aid, just saying that you may have talked yourself out of using SL5x5.
I am actually experiencing the opposite to irkie500. When I was doing my split routine, I leg pressed 350x3x10 and didn't get sore. The day after I started SL5x5, squatting 80 lbs, my legs were sore. I am going alot deeper on the squats than the leg press machine allowed me to get. Different muscles I suppose. The leg press also had me laying on my back, only lifting the weight. Squats has me lifting most of my 270 lb body as well as the weight. So there is a little more weight there too.