It depends what you want to do with it.
The Interspiro/AGA is very popular with public safety divers who practically wax poetic about it. For recreatioanl diving you'd want the demand version not the over pressure version. In either case they tend to leak some gas and one size fits most, but not all, with some fit minor differences between grey and yellow skirts, so one may work better for you than the other. Also the AGA is quite buoyant and needs a weigth kit to keep it close to normal.
The Kirby Morgan EXO-26 is a superb mask but big and expensive (about $900 without coms) and much better for commercial than recreational diving.
The Ocean reef neptune masks have gotten mixed reviews - some like them, some hate them. They are based on a gas mask design and that drives some of the negative comments whether it is a valid issue or not.
Cressi sub has made a simple FFM for about 40 years. It is inexpensive and works with your own regulator, but it is a bit primitive. There is no oral nasal cavity so it tend to lead to elevated CO2 levels under hard working conditions unless you leave the mouthpiece on your reg - an option that allows you to use the mouthpiece in hard working situations and not in others. It however does not offer com capability like all of the other masks.
The Kirby Morgan M-48 Supermask is perhpas the best choice for rec/tech diving. It uses your own second stage and has a detachable lower pod that allows the diver to breathe off another regulator without removing the mask and switching to a back up mask. They used to be sold by Oceanic/JMC scuba as well for around $400, but I don't think they are still available from Oceanic.
Hollis now makes a version of this mask with the data mask incorporated in it, but it is expensive - about $2500.
If you are diving a FFM (other than the M-48) and will potentialy need to access an octo, etc, you will need to be able to remove the mask, take the reg and then put on a normal mask carried in a pocket for that purpose. It takes some practice.
I have used all of them except the Ocean Reef masks and I prefer the M-48 over the rest of them.