the CETME will take a rugged scope mount that is detachable and returns to zero.
The CETME sight base lacks the saddle which is present on its first cousin, the G3 or its clones. As a result, the claw type scope mounts as used in the HK version will slide fore and aft on the CETME receiver. Bad ju*ju. Scopes will lose "zero."
+1 on the PTR91. For the money spent, you just can't do any better.
-1 on the "greater recoil" myth of the PTR91/G3 clone over the FAL. This is just not so. There is a difference in the character of the recoil, but a 308 or 7.62 NATO is the same cartridge, fired in either rifle.
-1 on the "better sights" myth of the FAL. The sight picture obtained with the globe and post HK style sight with rear aperture is a better optical arrangement than the simple "winged post" front sight with wobbly rear aperture of the FAL. CETME has similar sight picture as the G3 or PTR91, but the paddlewheel rear sight is not as good as either the FAL or the rotating drum of the G3.
+1 easier cleaning of the CETME or PTR91, assuming you have the right tools.
+1 inexpensive G3 magazines over the FAL.
-1 on reaching the selector/safety on G3 or CETME vs. FAL. FAL is easier to manipulate the selector than the standard G3 or CETME or clone.
+1 on mounting optic on G3, -1 on CETME (for reasons set forth above) -2 or -3 on FAL optics mounting. FAL optics mounting arrangement is a replacement dust cover with a dozen or so little set screws. If one removes the FAL optics mount/dust cover in order to properly clean the rifle, the optics do not return to zero upon reinstalling the dust cover. Huge PITA, so most folks leave it set, don't clean the chamber, or properly clean their FAL because of the dust cover optics mounting arrangement.
+1 on accuracy of G3 or PTR91, as barrel is floated. Not so on FAL. FAL shoots to different point of impact from bipod as it does from sandbag.
+1 on modularity of G3 over FAL. Easier to mount different accessory bits on G3, different stocks, different forends, better bipods, etc.
-1 on gas regulating "feature" of FAL. G3 will shoot anything you feed it, no need to futz around with a gas regulator. Other than the "on/off" feature of the gas plug on the FAL for shooting rifle grenades, there is no advantage to a "gas regulator."
-2 or -3 on destroyed brass with G3, absent a port buffer. G3 or CETME will shuck your brass into the next century, and if you can find it, it will be unsuitable for reloading, unless you have installed a port buffer. Port buffer is best $50 you can spend on a G3 accessory.
+1 on weight of FAL. Other than FALO, the FAL is lighter and easier to carry or throw around than the G3 or CETME.
In the end, however, it is whatever fits you best. If the FAL fits your frame and enables you to shoot better than either of the others, choose that one. I would put the CETME in a 3d place position relative to the #1 PTR91, and #2 DSA FAL. Other "kit" FALs have a hodgepodge of parts and their reliability and quality varies as a consequence, and they may be worse than the CETME depending.