Yes but then they still masq their hag to you and now you have 1 less masq to get rid of it. This also assumes that you are able to get above their hag.
For example:
Masq/Masq has a higher probability of colliding turns 3/4 than Hag/Masq. What happens if you collid masq's and they dont' collide hag/masq. Their deck is now 7 coppers, 2 estates, masq and hag + whatever they bought.
Your deck is now 7 coppers, 2 estates, curse, masq, masq + whatever you bought.
If you collide again, and they don't (again you are still more likely to collide than them), you can fall even farther behind. What happens if next turn you collide again, they don't, and they get a walled villiage plus another masq? You are in big big trouble.
What are the probabilities of the game going this way? I'm not sure, but I'd bet it's VERY probable.
This situation is way too complex to fully understand without simulations.
This situation is way too complex to fully understand without GAMES. This is too complex for a sim like any we have right now. Fortunately, I (and I'm guessing many of the other top players playing it) HAVE actually played these games before. The masquerader wins. I'm not personally sure if the double masq does this better than the silver/masq, but I know the silver/masq does it.
Let's look at it logically though. You talk about concerns of terminal collision, but this is only SLIGHTLY more likely in double masq than masq/hag - on 3/4 the only hands where it's different are if masq is in your first 5 (and would have been hag) and another is in the 6th/7th card.
Another point you don't bring up is that Masq/Masq will reshuffle a lot faster. I'm not entirely sure who this helps.
But the big point is that you talk about the masq deck having less junk in it, so it will have less junk to pass. You say this like it's a huge problem for the masq player, but really it's a good thing. Trashing crap is good, right? So... not a problem in total. Also, where the hag player passes their hag, the masq player will eventually pass/trash a masq.
But look at it this way. You have a masq and a hag in hand. Which one do you want to play? ...the answer should usually be masquerade.
Now, I don't think this is like a huge slam dunk win for the masq-ing player, and going hag/masq is not ridiculous or anything. I just don't think it's
as good.