In general, with subcutaneous injections absorption is a little slower, but no less complete. This makes the apparent half-life of the testosterone ester somewhat longer than with IM injections. In turn this means less variation in serum testosterone. In practice, with daily injections of a longer ester such as cypionate the difference is likely to be undetectable; you'll see serum levels for either method be pretty constant and about the same as the other.
The difference would be more apparent with once-weekly injections. Then the serum peaks would be higher for IM, and the serum troughs lower. But the average level of testosterone over time would be about the same for IM and SC at the same dose rate. As a disclaimer, these are general expectations based on theory and existing studies. You will find some contradictory anecdotes in the forums.