Let the OP make his own damn choice. Statements like "you will regret doing such and such are unfounded and simply confuse the person asking the question. They are merely an outlet for expressing biased opinions without helping the decision-making process. The OP has been leaning towards making a MM and will most likely end up doing so, there is no need to make (him?) start out the character with the impression that he is inferior before even starting his build.
Yes, the two classes have unique advantages and disadvantages. Marksmen, lacking Hurricane, are obviously not as powerful vs. single targets. But that does not make them a poor choice of a character. Marksmen typically handle training situations better than my BM does. They have a decent-sized arsenal of 4th job skills that are very versatile, as opposed to BMs, who can almost get away with taking every skill but Hurricane off their key settings, but suffer in situations where Hurricane is less effective. Marksmen also have the advantage of higher base damage, freezing (in addition to the archer's already quite large arsenal of disablling/stunning skills), and an easier time in 2nd and 3rd job.
MMs aren't as desirable as BMs at bosses, at least in the current version of the game, because they can't match the raw single-target damage of BMs. That's not really saying much. Few classes can. NLs with SE, BMs, and Heroes outclass other classes in terms of DPS by a significant margin, so that MMs are ignored. That doesn't mean that they can't still output a good amount of damage, nor does it mean that it's impossible to boss as a MM. MM still outdamage a number of other classes - DrKs, WKs (comparable to their holy weak damage), Shadowers, and all magician classes. Marksmen still have SE, so that makes them at least more helpful than all of the listed classes but Bishops and DrKs. Look at Devil's DPS comparisons in the Training Center Sticky and knock down every class except BMs, MMs, and DrKs a bit for having only 60% mastery. It's not nearly as bad as it sounds.
Yes, the two classes have unique advantages and disadvantages. Marksmen, lacking Hurricane, are obviously not as powerful vs. single targets. But that does not make them a poor choice of a character. Marksmen typically handle training situations better than my BM does. They have a decent-sized arsenal of 4th job skills that are very versatile, as opposed to BMs, who can almost get away with taking every skill but Hurricane off their key settings, but suffer in situations where Hurricane is less effective. Marksmen also have the advantage of higher base damage, freezing (in addition to the archer's already quite large arsenal of disablling/stunning skills), and an easier time in 2nd and 3rd job.
MMs aren't as desirable as BMs at bosses, at least in the current version of the game, because they can't match the raw single-target damage of BMs. That's not really saying much. Few classes can. NLs with SE, BMs, and Heroes outclass other classes in terms of DPS by a significant margin, so that MMs are ignored. That doesn't mean that they can't still output a good amount of damage, nor does it mean that it's impossible to boss as a MM. MM still outdamage a number of other classes - DrKs, WKs (comparable to their holy weak damage), Shadowers, and all magician classes. Marksmen still have SE, so that makes them at least more helpful than all of the listed classes but Bishops and DrKs. Look at Devil's DPS comparisons in the Training Center Sticky and knock down every class except BMs, MMs, and DrKs a bit for having only 60% mastery. It's not nearly as bad as it sounds.