Adam - I've got both 40T ATB general purpose blades and 50T ATB/R combo blades that are pretty much intended for the same range. Number of teeth is only one factor, but in general, I do find that the best of the 40T blades tend to leave a slightly cleaner cut and rip more efficiently than my 50T ATB/R blades but there are exceptions galore, so you can't make the generalization that 40T blades are better than 50T. All blades are not created equal, and a lot of it's subjective...there is no "Best" for everyone and every situation.
The burning could be cause by a dirty blade, too many teeth for the task, too slow a feedrate, a dull blade, and some woods just burn more easily than others. Some blades have a tighter side clearance angle too, which gives a more polished edge but can also have a greater tendency to burn. You can try raising the blade just a bit higher to help reduce burning. Higher quality blades are definitely worth sharpening. Keep them all clean.
My Infinity 50T is the cleanest cutting of any of the 50T blades I've tried and it's an easy blade to get good results with. It's as good or better IMHO than many of the better 40T blades, and just a is tad shy of the more expensive premium 40T blades like the Forrest WWII, Infinity Super General, Ridge Carbide TS2000, and Tenryu Gold Medal. My DeWalt/Delta 7640 50T is very good too. Is your Ridgid blade the Titanium series made by Freud (gold tone)? If so, that should be a good blade that's very similar to the Freud 50T combo blades, but it's not made for ripping thick hardwoods over 6/4". As Bill mentioned, a good 20T to 30T ripping blade will be more efficient. If all other parameters are equal (they rarely are!), more teeth tends to yield a cleaner cut, but poses more resistance to the saw, a slower cut, and a higher tendency to burn, therefore a high tooth count blade isn't good for thick ripping. A lower tooth count blade tends to not leave as clean of a cut but can rip through thicker materials very efficiently. The better 24T FTG rippers can still leave a glue ready edge, but they don't crosscut well so are generally limited to bulk ripping....one notable exception is the 30T Forrest WWII....it's got the same configuration as their 40T but with fewer teeth. It's hard to tell the cuts apart, but it's noticeably more efficient in thick materials, and even leaves acceptable crosscuts in most situations. It's a very versatile blade and is an excellent choice for a one blade arsenal used on a smaller saw for cutting thicker hardwoods. You don't need to spend a $100 on a good blade, but it improves your odds of getting a good one....just avoid the lower end stuff regardless of brand, and know what quality level you're buying and what the blade's characteristics are. Watch sales and deal alerts for killer bargains.
some good reading ...more reading