The "obvious reasons" are that Muay Thai is more effective both as a martial art and as a fitness sport.
I have done over 10 years of TKD in various forms and JJ.
Have never been to a Muay Thai class before but know what it's like.
I guess I answered it for myself. An extra hour of driving a couple of times a week is worth learning something "real".
First class is today, I'll post back here afterwards to let you all know how it went... hrmm... maybe I should take some photos and see how it changes my body in 6 months.
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