I don't have the 3-20 Schmidt, but do have the 5-25. I have looked through the 3-20 and think the glass is pretty close to the 5-25. I also own the 3-24x42 march. as far as glass goes, I think I would give the edge to the Schmidt. its just so stinking clear and crisp, but in all the models (3-20, 3-20 US, 5-20 US) its quite a bit heavier, and until you get to the 5-20 US, quite a bit bigger. I put the 3-24 march on my 22" 6.5 Saum and its a perfect match. I had a kahles k624 on it, and although I love that scope, it was just a little bigger and heavier than I wanted for that rifle. I wanted it to be more "handy", and with the march, it is. I would consider the Schmidt US, but honestly for the money and the added weight, I can't see doing it. I also do like the floating dot of the FM-1 on the march. its a pretty simple reticle and great for hunting. My Schmidt has the H2CMR reticle, which I really like too.
In the end, for a hunting scope that I will end up packing in, its hard to beat the March. I was worried about the eye box, especially on the x42, but it doesn't seem as bad as the reviews would lead you to believe. Its no Kahles (which I think has one of the best eyeboxs out there) but its not hard to get behind either. The parallax knob does have a short throw from 100-inf, but its not had at all to get parallax free. again, the internet keyboard commandos must be a little to picky and bothered by every little thing. not sure how they get out of their air conditioned house to even shoot with every little thing bothering them. LOL. The turrets on the March are great as well for a hunting scope. low profile and enough resistance to keep them in place. I haven't played with the US turrets, but from what I gather, they are pretty nice. I happen to really like the MTC locking turrets on my 5-25, especially since its on my comp rifle. but that's me.
The hardest part about the March is picking them up on a great deal. they only come up sporadically in the classifieds, and there aren't a ton of retailers out there. I think someone has a x52 ilum March for sale now, so that might be a good buy. And they are a good bit cheaper than the Schmidt US.
So, for hunting I wouldn't consider anything other than the March 3-24 or the Schmidt US (or even a leupold mk6 3-18). anything else is going to be to big and or to heavy.
between the march and the Schmidt. the march wins on price and weight, but prob gives some in glass. to be honest though you would prob have to get out the optics charts and sit them side by side to really tell the difference. They are just both so good.