There's the Flex 7, which is like a Proflex except with hard ears (bottoms may have been a different rubber as well, don't remember). But nowadays, whenever i hear the word "flex," the person is referring to the ProFlex since the Flex 7 isn't exactly made anymore. Although all these belong to the Spectra series of masks, dunno why they don't use the Spectra name more.
JT Proflex as stated is the Flex 7, with foam ear protection.
I prefer the flex 7. IE Proflex with hard ears. They are easier to grab with my hands and since they bolt on to the front half of the mask they aren't flopping around all over the place. I feel like a girl adjusting my hair when I have to dink around with my foam ear protection, so I run the flex 7 ears.
If you are not going to use the visor on the flex 7, you can cut off the top portion of the ears to make them flush with the rest of the mask. Proflex ears used to require this cutting, but the new ears (as of like 6 years ago) don't.