I can't see any difference, what makes them have a diff. name?

Does it have anything to do with the target knobs?

M3 also has a ballistic cam to indicate drop at each distance.

Guys, I appreciate the replies.
CSGunWork, do you sell these scopes?

About the M3, is it better since it has the bullet drop distance thing, that's the feature I am looking for, is the M1 different, or would you have to do it manually ( think of the bullet drop and click it in)?

Quoted: Guys, I appreciate the replies. CSGunWork, do you sell these scopes? About the M3, is it better since it has the bullet drop distance thing, that's the feature I am looking for, is the M1 different, or would you have to do it manually ( think of the bullet drop and click it in)?

Being better would depend on your use. The M3 is not as percise as the M1 since the 1moa clicks are very corse. It was originally made for quick adjustments on human size targets. I like the M3 as I do most of my shooting against steel targets I made out in the desert and I don't mind if it hits dead center on the target or 3 inches low. The 1/4 clicks of the M1 are better suited to putting the shot exactly where you want it.

The BDC cams will get you in the ball park but they are made for specific weight bullets and velocities. Depending on  your evelation, weather conditions, loads used and barrel lengths it can be off quite a bit.  You can get cams made for it by Kenton industries if you want one made for the exact load and other conditions.

Quoted: About the M3, is it better since it has the bullet drop distance thing, that's the feature I am looking for, is the M1 different, or would you have to do it manually ( think of the bullet drop and click it in)?

see above.

in a nutshell:
shootng at paper?  M1
shooting at an enemy?  M3

note that the M3's stock BDC (55gr .223 3200fps) is probably not going to be suited for whatever round you are using.  so you'll still need a dope chart OR you have to buy a BDC dial calibrated to your target round.  one advantage of the M3 over the M1, however, is that it is a single turn from min to max.  this makes it harder to "get lost" while under stress (like on a two way range).  you need to pay a little attention on the M1 so you don't end up one full turn off from where you think you are.  if your round hits about 3 feet high you know what the problem is.

one other item to note (and remember at the range):  
the M1's elevation and windage are BOTH 1/4 MOA.  
the M3's elevation is 1MOA and windage is 1/2 MOA.    

pictured below is an Illum MR/T w/ M1 dials.

ps:
PLEASE, whatever scope and mounts you get, lap the mounts with a 30mm lapping bar.  any mounts, including Larue, will be improved (trued) with 20mins worth of lapping.  

ar-jedi

Just to confuse the issue a little more Leupold will also swap the M3 evelation guts for the M2 which are a 1/2 moa for a price but you would have to check with them to see how long and how much. If they sold that set up on the 3.5x10 off the shelf I would pick one up as it seems like a nice comprmise between the 1/1 moa and 1moa knobs.

Just to add more imput, my Leupold 3-9x36 MR/T M3 elevation turrets are calibrated for 62gr. 5.56 bullets.