I have both a 26 and 22, while the 26 may not sound much larger, it is. It is also double the price. If you could swing it, I would get the 26, also if you do any indirect cooking you will have a lot more space on the 26. I think a 22 would be fine for most occasions though. The 22 has been feeding families for decades.
XL Big Green Egg, Weber Performer Platinum, WSM 22.5"