From my point of view it depends on how many 4/5's you already have to use with smaller tools like drills/impacts, etc. I'm now buying only 8's as I find for me they work out so much better for stuff like the RSC, KHC, saws, etc.
I only have the drills - TID 18, T18+3 and T18+3E, and for whatever reason, I'm not currently keen on the other cordless. Though, since it's being discontinued in NA, there is a wonder if I should get the AGC.
The AGC is nice, but to my mind it's sorta a little too niche unless you're planning a fair amount of tiling/concrete work, not to mention it's pretty expensive for a unit that doesn't work with a track.
