I have a 7 foot medium for dropshot shakey head.  I will be putting 7 pound fluoro on it.  wondering whether to pair it with a 2500 or 3000 size reel

I use a 2500 for those techniques, it works great for all my bass fishing needs.  The 2500 should be a little lighter as well.

The difference between a 2500 series and 3000 series lies in the line capacity. The 2500 is more than adequate for 7# line.