I would never need 2400W. But if you wanted 2400W, the Crown XLS-1002 could be bridged to get 2400W for $260.
There is no reason why an Internal Amp would Outperform an External Amp. The Only difference is that one amp is Internal and one is External.
Some internal sub amps do have nice Sub EQ features. If you are willing to pay the premium, you do get these nice EQ features. But there are other ways to get EQ as well (although probably not as fancy). I love what Audyssey Subwoofer EQ does for me (Audyssey Dynamic EQ is a must-have feature to me).
Companies like RBH & Funk are 2 companies I know of that offer both internal and external amps for their subs. And their sub amps have very nice EQ features that may sound better than Audyssey SubEQ.
But I'm kind of cheap and I already love the way Audyssey Dynamic EQ does for my subs.
I personally prefer an External Amp because if the amp ever fails (electronics fail more often than drivers), I can easily switch out another external amp.
But comparing prices between ID vs B&M can be tricky. Like in the example I gave, you could get a RBH SV-1212N (non-powered) sub for $1200 (or less) + $260 Crown = $1560 delivered (or less).
With the JTR, that's $1900 + another $200 shipping depending on your location.
So the question is, what's salient to you? Maximum excursion performance to break every glass window and hurricane clip in your house? Or a balance of performance + aesthetic WAF + price, etc.
I will always prefer externally powered amps for subs and speakers because I prefer the ability to easily change out my amps.
A lot of variables to consider and more than one way to do things.