What's harder? Getting punched in the face obviously, followed by having your legs repeatedly kicked. Dry-humping and wriggling around on the matt in the most undignified positions imaginable doesn't even compare.
Why are we talking one versus the other? Striking and grappling are of course not mutually exclusive. If she is interested in mma then I'd suggest that she joins an mma gym and will train all facets. What is the motivation to narrow down the training?
BJJ is less dangerous..however your going to have allot of guys having your wife practice the triangle 30 times in a row.
some truth to that.....but allot of mma gyms that try to teach everything tend to be jack offs of all trades and masters of none.
well when you start doing muay thai you will learn how to stand and give a 1-2. well when you start doing BJJ you will learn how to sweep. Neither are dangerous when you start.
striking is much more dangerous cause of the blows you take to your cranium in grappling you just tap thats not the case with striking