I had nothing but problems using SLA batteries for my ebike. After buying my 3rd pack of batteries(~$120/ each battery pack-3x 12V20A) within a year and a half. I thought to myself I could buy 3 more packs for the next year and a half (~$400) or get a LiFePO4 and have it last me for three years.

The problem I dislike the most is if you are not 100% on your charging/recharging cycles, you will notice a decrease in range through sulfuration. Each couple week, you'll notice another mile lost on range as sulfuration increases in your SLA pack. I went from 18miles on a single charge to ~ 6mile per charge, and it steadily got worst: 18, 17, 16, ....6 miles, then I would have to buy another pack. On the other hand LiFePO4 simply rocks, the range IINCREASED with each charge during the break in period, I could lock up my ebike for hours while not charging, and not worry if it lost range, awesome sense of freedom. It changed my ebike from a gimmick toy ( do I want to ride it today not knowing if I lost a mile in range from charging overnight?) to a workhorse that I can rely on...there are more benefits to LiFePO4 than what I mention, but I think you know them already.
SLA-High maintenace, very heavy, noticeable lost of range within months.