As Lucky pointed out, JJ is the 2nd best WR on this team. But, he has yet to live up to his potential on the field. He's got good size with excellent speed, but he hasn't been able to remember where he left his head when the game starts. In my opinion and, it appears in the coaches opinion, JJ may be turning the corner. If he has, then he makes the perfect #2 WR to compliment AJ. I could see Walter moving to the slot position, because he's bigger & stronger than JJ, but not as fast. With AJ & JJ on the outside the Texans should be able to stretch the field more & open the over the middle routes up for Walter, Daniels, & Slaton. It'll be virtually impossible to cover all 5 of those players.
Assuming JJ has turned the corner (and I believe he has), it's my opinion that the bubble list changes to AJ, JJ, Walter, Davis, Anderson. Thus, my original question of who you would rather keep (Anderson or Martinez) would be a legitimate one.
Both Anderson (3 years) & Martinez (4 years) have had a bumpy career & both have had some success. I like Anderson, but it's my opinion that Martinez has looked better this preseason. Much like Davis & Walter before they became Texans, Martinez hasn't been given a lot of chances on the field to show his skills & both of those players have worked out well for us.
The bottom line is, I think Martinez is an upgrade over Anderson. But, that's just my ignorant opinion.