I think it's more from a marketing and new vs. established company rather than the technical merits of the products. Griggs and MM have been around for some time, and they're products are proven and well-reviewed. I had a torque arm in my basement but sold it before putting it on the car and put in a 3-link. I've typed up a review and I've been sitting on it for too long now. Suffice it to say I'm happy with the way it works and the guys at EVM very much stand behind their products in terms of answering your questions and after the sale tech support.
Don't know about class legality - I do open track/DE.
'87 GT Griggs front, EVM 3-link, Brembo/Baer, GT40 heads and intake, panhard, coilovers, Kirk Racing Roll Bar