Just my opinion, but I wouldn't be interested if it requires two wrenches to tighten the collet (and I imagine change burrs/bits). One, or none would be much more desirable!
I completely agree, If you have basically 1 handpiece at your
bench, get a quick change handpiece (about $125.00). It’ll pay
for itself in days, not months or years! Save the other for some
task that doesn’t require frequent bit changes ( more than 1 per
week). I believe the description of the AMT indicated it was
Foredom Compatible, to me that means the handpiece can be snapped
off/on (among other things) A flexshaft is PITA if it’s a chore
to change bits.