Crye Precision developed the first version of their signature Combat Shirt, it would lead to widespread adoption as an alternative to the traditional BDU. After it was released companies like Massif, Helikon-Tex, and Tru-Spec came out with their own variations on the design. Of the designs, I felt the Tru-Spec one was the most watered down. The lack of a Zippered Mandarin Collar, fewer storage options, and a generally weaker design overall didn't pique my interest.
However, Tru-Spec has recently improved their design with the "Xtreme" Series. This lineup is much closer to Milspec designs of the other Combat Shirts out there. It still manages to retain a cheaper cost than the others, which makes this kind of system much more affordable for the player with shallow pockets.
earlier designs, those are still readily available and retail around $60. I currently own a custom-made Woodland MARPAT Combat Shirt and a genuine USMC FROG Shirt (similar to a Combat Shirt), but I've been thinking of picking up another with the warm weather we tend to play in. The Tru-Spec "Xtreme" Combat Shirt looks like a good option for me.