In fact, unless you really, really focus on keeping the hips down, shoulders high, and toes pointed–the leg curl is close to useless. Maybe as a super-set closer, but still you ned to key in on form to get any benefit.
I would say Good Morning too. Although that’s nothing wrong with leg curl in general, I personally think that martial artist should avoid training lying down on a machine (lying machine leg curl) or sitting down in a machine (seated machine leg curl) at least for most of the time.
Exception to the above would be those who have underdeveloped posterior chain.
I would go for GHR for knee flexion, and GM, SLDL and cable pull-through from hip extension.
I don’t like GM’s as a ME exercise cause I tend to overpower my hamstrings and use my lower back which is strong enough. But using it with lighter loads and higher reps (ie, 6-8) it is a GREAT assistance exercise for me and has greatly brought up my hammies.
In your case between the two exercises i’d choose Good mornings, i feel RDL’s hit it a bit more…
GHR is THE exercise for hamstrings, if you can even try practicing the manual one’s its something at least (and hell of a feat of strength).
Another exercise I like is Snatch Deadlifts off of a box… recruit’s posterior chain and hip flexors like CRAZY cause you’re ridiculously deep.