In the past month, I subjectively listened to 1.7MG and 8361A in different settings. The comparison may seem a difficult task as one is planar and the other is coax, especially in different settings. But no, it's a very easy comparison: go for the 8361A if you can.
Subjectively the 1.7 MG sounds extremly weak and somewhat strange (distorted and possibly with interference) if pushed against a wall, especially in mono. In stereo and in a further away from the wall setup, 1.7 MG can sound nice on some tracks when sitting in the right spot, even more so with some room correction and a "matching" amp (some give really bad results with 1.7 MG, as I have experienced with swapping amps, especially in the highs). Some MG owners seem to manage to produce interesting in room response, probably at the expense of spending an awful amount of time (and sometimes money too) in doing so and are never fully satisfied as they always are looking forward to upgrading to the next bigger MG, whichever model they have. Many add subs, which can sometimes be very complex.
But the 8361A just sounds big, alone, in mono and even with no correction. It's easier to steup and so much more powerful, not to say it can fit on a bookshelf (a big book shelf, admittedly). Magnepans don't stand a chance in blind testing comparison, IMO. Just not the same league. The precision of the reproduction of 8361A doesn't let bad mixes or recordings get away with it, which may require being more picky with version quality. But I find it interesting to hear what has gone wrong in the track exactly, and being able to discern which recording sucks and which doesn't. 8361A sounds a little bright to me, but highs can easily be dampened in GLM (in just a click). The sweet spot can be wider with 8361A too, thanks to the coax design it seems. I moved about in the test room to check.
As far as measures are concerned, Magnepans always have scored (very) badly, whereas 8361A is top level (state of the art?).
As far as price is concerned, 8361A may look more expensive than 1.7 MG at first, but they already have amps built in (and even a DAC as a matter of fact). So when all things are added up, if you buy it all from scratch with decent preamp, amp and DAC, the price difference should shrink.