I have seen people on multiple forums talking about how st croix rods are a little stiffer than their rating. I'm wanting to get a medium power spinning rod. If I were to go with the mojo bass should I get a ML instead of a M?

I wouldn't necessarily say they are overly stuff for their rating, but I guess they are a little on the stiffer side ( which I prefer). I think you'll be fine with either power

I have a medium legend tournament spinning rod (wacky rig model) and a ML Avid spinning rod. no mojos but in my opinion the medium is slightly stiffer than other rods and the ML seems to be pretty accurately rated. I would definitely stick with the medium if you are looking for a medium action rod though ML is probably not stiff enough for what you are looking for.

I think they're stiffer than others.

I had an Avid 6'3" MXF which I thought was
too stiff. It broke, etc., and I ended up sending
it back and upgrading to a 6'3" MLXF Legend
Tournament Walleye spinning rod. Holy COW
what a difference.

Perfect spinning rod so far. Love it.

Look at the lure weight ratings instead of the power label to get a better idea how the rod will fish. St croix's idea of m, mh and Hvy tend to be a little heavier than others. 

They are a bit under rated as far as power goes, but if you were looking to buy a medium in another brand, I'd still buy the medium St. Croix. Check the recommended weight on the blanks to be sure it'll handle what you want, but it should be good. 

I would stick with medium if you want a medium, they may be slightly on the stiffer side but not like some companies where they are waaayyyy stiffer, aka abu!

Like they said. You might want to focus on the weight ratings. A St. Croix medium fishes a little "heavier" than a medium rating according to a lot of other companies (not so much others, see Abu Garcia, etc...), but if I were specifically looking for one typically thinks of as a medium rod, I'm not sure the medium-light rod will be quite what you are looking for. You might fall in between. To be fair, I'm not as familiar with the Mojo rods, but a MXF St. Croix might toe the line just right, depending on what you plan on doing with it.

The medium spinning rod will suit you well for bass. i use an avid and an ltb in medium for spinning set ups and they are great 

Stay with the Medium Red. You'll be happier that you did! IMO a little more versatility! If you buy the new models of the Mojo Bass they just upgraded the blank to a SCIII so their a little bit lighter (15%) than the order generations of Mojos SCII. Either way their both good rods!

It would depend on what you're using it for to me as well as which model you're getting. 

My observations on St Croix powers are: there is a power missing between ML and M in their freshwater lineup.  I filled that gap with their inshore ML.  I discussed that with Jason Brunner of Croix a couple years ago and he agreed with my findings.

Depends what your baseline is. If it's St Croix everything else might be a bit off. 

I have an Avid and a Legend Elite. BOTH  of them are stiffer than their ratings and I had to adjust what I was planning to use them for. 

Thats why , yesterday ,I ordered an Inshore Gulf Coast Rod one action LOWER than I wanted .  Quite a savings on that Rod directly from St Croix. $150 for a $300 Rod!