One of my favorite lures to throw has got to be a squarebill crankbait. I'm heading to bass pro within the next few days to finally pickup a crankin stick for squarebills. I was originally going to go with the 7'M but am now considering the 6'6ML for the smaller crankbaits I own. I fish mostly local ponds with my buddies but I also own a boat and occasionally hit the bigger lakes. My question is would a medium light rod be okay in the bigger lakes? Or should I just stick with the medium? I just feel like I wouldn't be able to cast lures like a little bomber square A very far with a medium without a birds nest.

I use the Bomber Square A on a MH, it weighs 3/8oz and even the smaller one weighs 1/4oz so there shouldn't too much of a problem. I have a Fenwick Aetos 6'6" ML-M cranking rod, I consider it a finesse cranking rod and I have it specifically for throwing smaller cranks up to 3/8oz and I love it. The problem is cover, you said square bills and if you fish them in cover you'll want a MH rod, if I'm fishing for big smallmouth in the river when I'm just hitting rocks with my square bills then I go with the medium light for my square A and KVD 1.5s along with Manns Baby X and 1 minus cranks. If I'm fishing a lake and my square bill is going through brush and I'm ripping it free from weeds then I'm using a MH as I need a little more back bone and I'm using a rod that is moderate fast, not a full parabolic action, it takes too much effort to keep trying to pull square bills free from cover with a rod that is too soft like a ML.  If you aren't going through much cover look at the size baits you are using, if you are throwing anything 1/2oz with regularity then go for at least a medium, I have a medium light as I already told you but that is because I also have a medium and medium heavy, for me it was about getting a rod that is dedicated to fishing smaller cranks in certain situations.

Usually  a longer rod is easier to get distance with than a shorter rod.  You are asking about power but you need to consider action as well.  If you watch the pros fish cranks they use moderate actions instead of fast.  The reason given is that the slower action is more forgiving on the strike and fighting the fish, leading to fewer trebles ripping out.  I really like a moderate action.  Actions like this are usually called crankbait rods or actions or popping blanks or actions.  They are , in my opinion, best suited for the cranks and not for jigging, drop shot, or other techniques where you want more sensitive rods.

 

As for power it all has to do with matching the lure rating of the rod to the weight of the lures you plan to use.  If the rod does not load properly it will be more difficult to cast for distance, and I believe less easy to avoid backlashes because you are pushing it.  It is better to go over the lure rating and cast more gently than to push a too  powerful rod down to lighter lures.

Look at the lure weight range and less at the designation M/MH/ML. Etc they are too subjective

I have a 7' medium bps crankin stick and I throw any squarebill crankbait I want to. Including a lot of square a's