March has different appeal for different shooters. I helped a guy out here on the Hide last year, he bought both the ZCO 5-27 and the March 5-42, he ended up feeling the ZCO was better in just about every way. Another guy I helped in May, same situation, he ended up buying ZCO 5-27 and March 5-42 and his opinion was March was way better. The March is a very short scope with an 8.4x erector, there are going to be some hurdles to overcome, but if you're aware of those shortcomings and prefer a short scope then you'll be pleasantly surprised. The edge distortion on the March 5-42 bugs me (as it does on most scopes that have edge distortion), this is something that the 4.5-28x52 scope manages much better (than the 5-42). If you're looking for pure optical performance, TT - ZCO - Minox ZP5 pretty much rule the roost. If you want greater FOV, magnification, shorter scope, etc. then you'll be looking at other scopes.
Based on early reports it sounds like the Leica may be close to the ATACR optically, but with much better FOV. Now that Leica has a much better warranty (transferable) they are more appealing because resale won't leave the new owner out in the cold.