I personally would say a MM is more fun to play but it has it's downfalls with bossing which makes it a more difficult class. However, a Bowmaster is much easier since you just need to tap one button to hurricane. In addition both classes require a minimum of 5.6k hp in order to horntail (with HB). This can easily be achieved with leveling up with just int gear and not adding any base int. If you want to aim for high hp you will have to add ALOT of base int which can be a costly procedure, i would suggest you create a bishop first in order to raise the right funds to reset all that int if you set to aim for 10k+ hp.
If you want to take the new source into consideration, I believe HT will be 9k(?) minimum. BM has better damage hands down. My friend really enjoys his MM, but you will always lose to BM's in terms of dmg. But you have that SE so you will never lack parties ^^
9k damage is for legs magic attack, which is why ideally you'd wash to 5.6k and have HB. Your ranged attackers shouldn't be the dispel targets so there shouldn't be any worry about losing your HB unless your drk is forgetful
If you find hitting the damage cap often as fun, go for Marksman. Fun is subjective for me. Bowmasters are by far easier because you won't need to track Snipe cooldown to optimize DPS. Both need to HP Wash the same amount.
The reason I'd go with BM is because bows look better than xbows. I don't like how xbows cover like 70% of your character. #LooksMatter
I thought that ranged attackers typically don't receive HB since they're positioned on the opposite side from the DRK? Or perhaps there's another efficient HT setup that can constantly provide HB to the ranged attackers? On topic though, I went BM over MM because it's flashier and better in DPS.
When we were doing our first runs before we learned about freezing body parts (which is relevant because in new source parts won't be frozen), we had a drk stay on the right side with ranged attackers until tail was down. Once tail was down, depending on party set up we (if we had stronger warriors) would go up straight to wings. Generally the longer the warriors can hit multiple targets at once, the higher DPS they can put out.
I use the Hessonite Saber cash item because it doesn't block my face, and the weapon's animation is the same color as Soul Arrow.