I want to get a cumara for my next rod, however I'm not very familiar with shimano rods and how to gauge their powers/actions.

I'm looking for a rod to throw 3/8 t rigs and jigs. The two I'm looking at right now are the 6'8" mh fast and 6'8" mh xfast.

Which rod in this series would you recomend?

Mike, for what it's worth, I own a 6'8" mh xf that I initially used for 3/8 -1/2 oz jigs. It's a great stick for jigs, and is extremely well balanced with about any reel. I also have a 7' 2" mh xf that I use for t rigs. I like the extra length for bomb casts, and I have learned that I like working creatures and such with a longer rod also. I think the xf rods work the lures better, but they fight the fish well also. Both rods also have plenty of power and are tough as nails. That said Shimano has changed there warranty to one year vs.the lifetime warranty they used to have, something to consider. On a side note, since purchasing the 6' 8" cumara last year I have upgraded it to a 7'1 nrx, not that there was anything wrong with it , I'm just a gear junkie like the rest! Hopefully you have a shimano dealer near by to see for yourself. Rip some lips brotha !

This is just me, but I would opt for a tad bit longer rod. 7' to a 7'3. I have a 6'8" rod that I have used for jigs before and it's not that easy to set the hook on long casts. I have to tighten my drag all the way down and yank as hard as I can lol. I would go with their  7'2" MH Extra Fast