Hopefully my comments can help you, ive had experience with the vandy 1c (dad), and personally own mg12s and martin logan requests (more range, same ML house sound).
Vandy 1c - these are a pleasant speaker, (especially after some mods). Phase correct. In my opinion the two way design is somewhat of a tradeoff, the midrange is not really magical in the same way the logans or the 12's are. Dont get me wrong the 1c is a great speaker, it does it all, has no glaring flaws, no nagging annoyances, and covers a really good range. However you make some tradeoffs asking the woofer to play both mids and deep bass. Great value - Especially used. Personally I don't think they look that great... matter of taste.
The mg12 is a great speaker. Placement can be hard, and it can be a frustrating speaker if you do not have ideal room acoustics (same with ML). It balanced, bass is just barely low enough to live without a sub, but I was happy for a long time with careful associated equipment and placement. Its hard to integrate a sub seamlessly - even a good sub. The mg12 is a really special speaker in the ML lineup, its not as smooth as some of the other speakers but has a somewhat gritty musicality to it (not grainy). They really smooth out with some mods. Great speaker. The 1.6 maggie loses some of this musicality though... not sure why. Everyone says maggies need a lot of power, I call BS, I had great results with my tube amps. (I do have some serious solid state power also - bryston 7bST ~800watts rated down to 2ohms)
The ML are a different type of speaker all together and they really sound it IMO. ML has really gotten good with bass integration - better than you could ever do with an aftermarket sub. The ML sound has this silky smooth magical sound. Its unlike any other speaker i've heard, its like the sound is alive and 3d. There are downsides (no free lunch). THe stators wear out after about 10 years and need replacement, they need periodic cleaning and vacuuming. They have wicked impedance curves and eat amplifiers for lunch. My requests are particularly bad - the newer speakers are a lot better but still require muscle.
The bottom line is the ML and the maggies are both winners. The maggies can be had used for pretty cheap - just make sure they are not coming unglued (problem magnepan had in the past). Sometime after I bought mine they switched to a white coating / glue which is supposed to solve de lamination.
