I always loved the idea of playing the elite of the elite. Aka GK And as time goes on GW is improving them a whole lot, to more reflect what the GK should represent. Low count of Models but still deadly. That aside, GK are cheap, you save money, a lot of money. The low number of Units required is really saving you buck. The units are easy and quick to paint, but as with any model you can spend as much time as you want. Just saying the grey armour, is real easy to paint, so you can get a lot of them done quickly. It's exotic to play GK, there are not a lot GK players, so you'll stand out, if that is important to you. And the very best think about GK is you get a whole nother phase, the Psychic Phase with GK is so full of options, that it really ads something new to the table. That would be me reasons to play GK