TA to TC MGs had a spindly look, whereas TDs and TFs were given more solidity. Length was increased from 140 inches (3556 mm) to 145 inches (3683 mm) and, more importantly, width from 56 inches (1422 mm) to 59 inches (1499 mm). Wheelbase remained the same for all versions. MG T-types were attractive in their way, regardless.
This was the MG that first made an impact in the USA.
TDs (1950-53) were more common.
An effort was made to modernize the styling while the new MGA was under development. The hood now slants downward and headlight assemblies are attached to the fenders. Some people criticized this at the time, but I didn't mind the change then, and don't now.
There was little difference over the three initial series roadsters.
The TD's added length seems to result in a less-vertical trunk and spare tire mounting.
The front fender has a wider, flatter top to accommodate the integrated headlight assemblies.
Compare to the image above. The added length is in part between the aft door cutline and the rear fender. The rest appears to have to do with the angle of the trunk and spare tire noted earlier.
The hood slope can be seen here: compare hoods at the point of maximum front fender height.