Dwell at TDC?

That's going to be a big shoehorn :D.

If you think of TDC as the time the piston and rod and crank journal are all in a stright line, then you're not seeing the whole picture. That's because the crank and rod are turning. So the piston reaches TDC a few degrees before the crank and big end of the rod do. It also means the crank and rod are past TDC before the piston begins to move down. The longer the "levers" you have in a given amount of space (connecting rod and crank throw in this case) the longer the dwell at TDC. What this means is there is more time in terms of milliseconds for the mixture to be ignited and begin to expand prior to the piston being able to be moved. If you've tried, you'll note you cannot push a piston down when the crank throw and rod are straight at 90° to the crank centerline. In most naturally aspirated gasoline burning cars, a longer rod will give you more low end off idle and a shorter rod gives you more top end power. That's incredibly generalized. But hopefully you get the idea. The problem comes if you are running pump fuel and a lot of ignition timing. If it happens too early, the pressures in the chamber get too high while the rod is still basically "straight" and the bearings and mains get the crap beat out of them, the chamber temps get much hotter, and the propensity for detonation and pre-ignition go way up. Personally, I design and build for the fuel type I need to run and as much stroke as the person will let me with the longest rod and a piston combo I can get that is no shorter than 1.45". The benefits of stroke are easilly recognized. The benefits of rod angle and length are much harder to "see" or feel and in most street engines are not that important.