I recently broke about 4 inches off of a 6’6” rod and after replacing the tip, I’ve decided to just buy a new rod to replace it. I generally used this setup for plastics like tubes, Ned rigs, and other finesse approaches. I am leaning towards another medium action, but should I consider a medium heavy? It will be used for both largemouth and smallmouth, but will get a little more work targeting largies since there are more lakes around me with them.

100% M. This question is usually M or ML. With more details about what your arsenal looks like and what "other finesse approaches" means to you I might even say ML.

Medium power with a fast or xfast action. 

M

Medium. Wait. Just how big of a Ned/Tube are you slinging??

Between the two, M for sure. But I like ML personally when talking about "normal" ned rigs. 

As we often discuss, M, MH etc are subjective terms with no industry standard to define them. For example, two rods may both be rated to cast 1/4-3/4, one labeled M and another MH. The MH may have more backbone making it a better choice in heavier cover. Look at the lure weight rating first, then think about the cover and be sure you have the power you need. Whatever designation the manufacturer puts on it means little.