Iv'e had the 3pks and Mars R, and currently have a Helios and ex1 ur.

3pks- great radio, never had a problem with the FASST system, but it felt like the leaning tower of Pisa, a very top heavy radio. Comes with a tx battery but it needs to be charged between rounds. Probably the easiest of the 3 to navigate the menu.

Helios- trigger throw took some getting used to as it's a little more than the 3pks. Jog dial works great. I"m using crystals without any problem. I just wish it was a tad more compact. It'll tip very easily on the table.

EX1- smaller radio so it's better suited for smaller hands. Mine is still sitting in the box so I cant' compare it with my other radios other than the Mars R, which is basically the same thing. KO's new 2.4 rx is just slightly larger than a postage stamp.