DHW Mapsets vs. Map of the Month for best/most fun...well, I have to say I find a tough call there. I think I'll explain by making as thorough a comparison as possible (note however I've only beaten the June and July 2007 MotM games), and feel free to respond with what you think. This is going to be a big post, I'll say that right off the bat, but I hope it's a constructive comparison that some good discussion can come off of. So here we go:
Let's get the most obvious thing out of the way before we even start: The DHW Mapsets are in SDL, while MotM isn't. I'm not going to call that an aspect of the contest per se, but it is definitely something I will mention before moving on any further.
So - First of all, coding. Clearly, the MotM's have more code changes (not hard, since the DHW sets have basically none except for episode names, title/intermission screens, and par times). MotM on the other hand features shading in every release, completely customizable floor/ceiling colors, a crosshair, a different status bar, and level names displayed at the start. That's for June and July; for August and September, more keys, the ability to block an enemy from moving through a space, and switches that trigger things in the level were also added. Then there's the stamina bar in October and November. First of all, to get it out of the way, I don't like the stamina bar; I can tell you that in advance. I like to run and the game is simply going to be less fun if I can't run at least when just going through rooms; there's no two ways about that. On the other hand, every other feature certainly introduces the potential to add to the maps. So that can be considered a plus of MotM against DHW Mapsets; there's more features to use.
On the other hand, occasionally a feature is abused, like I can't for the life of me figure out how to get August 2007 started because I have no clue how I'm supposed to deal with the big room in 'Facing Hell' that has all those enemy block codes. And it's the first level in the set! I mean, I know there will be great maps but is it like they didn't want me to play it? That said, that's the only example I know of so far of what I'd consider a feature abuse, and it may be open to reconsideration of someone lets me know how in the world I can make it so I have a fair chance of getting the level started. It's by Thomas - I mean, would he EVER design a level you can't play because it's too hard?
Secondly I'll address what should be a shorter point: release formats and consistency. For the DHW Mapsets, that's easy, because both were released exactly in the same format except one is for Wolfenstein and the other for Spear. But for MotM, there was an different EXE for each pair of months in the six months total. This means some sets could take advantage of features others couldn't. Not necessarily good or bad on its own, because it depends how these features are used. But I will reiterate that the stupid stamina bar in the last two is practically a guaranteed negative for me right out the door.
Thirdly and finally, the mapping quality and consistently itself. I find it hard to believe there could be a single bad level in the DHW sets; every author involved in them, with the sole exception of Hellblazer who made three of the SoD levels, is clearly a very good level designer. All of them have either made a very good set of their own before contributing or made good contributions to other community sets (including but not limited to MotM); most of them had done both. So you know each and every one of the 81 total levels (60+21) you are playing (with the possible but by no means definite exception of Hellblazer's three maps in SoD) is by a designer who clearly has plenty of experience and knows how to make one good (or very good/even excellent) map after another.
On the other hand, MotM has a lot of contributors who make somewhat lesser levels, and are not well known for making plenty of other levels beforehand. This even includes a few authors who contributed to the DHW sets but clearly had time to develop much more experience by then. So consistency of quality, while generally fairly good from what I've played (again, the June and July releases), is less definite. In addition to 'Facing Hell' which is shocking me because it IS by an author who had already had a ton of great work out by then, you have something like Level 10 from the July set. Frankly, that map sucks; it is unreasonably hard (for no good reason at that) and design itself isn't anything to marvel at either. And there are other levels that don't suck, but hit me as merely okay or pretty good. Then there's the excellent levels, and there are at least a few in each set. Look at the order of winners, if nothing else. You know the top couple of places, at minimum, are pretty clearly going to be great levels. But I'd say it's also a pretty safe bet the mapping quality is going to jump around more than in the DHW sets.
That pretty much concludes my comparison; I am not going to make a clear conclusion for which is better and leave it open for negotiation instead, but I do feel I've presented the individual strengths and weaknesses of each.
As a final note, however, to those who do respond with MotM, I'd be very interested if it's referring to all the competitions or just because of ones from certain months. None of the sets are bad; they all have at least a couple very good maps too, but similar to between levels/episodes, I don't think the quality between sets is completely even. So I'd like to know which months one enjoyed most, more so than the DHW sets especially if they choose MotM as the best of all the community games (including ronwolf).
Anyways I hope I stayed on topic and didn't bore; I am/was simply trying to produce a constructive, analytical, and in detail comparison of factors that I feel should be considered. Any and all commentary/discussion in response is welcome.
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Also voted for the DHW Mapsets and BMSE Anniversary edition.