Stone, to a large degree yes fine grain and sharpness (you could call it crispness) are at opposite ends when balancing a developer's characteristics. It gets a little more complicated with more dilute developers where edge effects come into play, but don't worry about that. Just know that generally the finer grain a developer is formulated to produce, the less sharp the edges of the grain will be.
Originally Posted by StoneNYC
Most general purpose solvent developers like D76/ID11, DDX, XTOL, TMax RS, Ilfosol etc etc are designed to give a good balance of both fine grain and good sharpness, without going too far in either direction. Developers like Rodinal, FX2, Beutler, and Pyro favour sharpness over fine grain. Developers like Microdol/Perceptol favour fine grain over sharpness.
The differences become a little less clear if you alter dilutions, agitation etc. Generally the more you dilute a solvent developer the sharper it will get, with the tradeoff of higher graininess.
What I would say is that from a grain or sharpness perspective you won't have a whole lot to gain or lose by switching from Ilfosol to DDX or TMax. What DDX or TMax RS offer is somewhat higher speed, at least with tabular grained films.
How you use the developer is important and gives you some flexibility with respect to graininess and sharpness. And of course you can also control contrast (and film speed to some extent). So it is more about how you practice using the film/developer combination than switching developers. Many of the differences between similar types of developers are quite small. So I would not consider yourself limited in any way with Ilfosol. I have not used it myself but I'm sure it can do whatever you need it to do.
If you want to learn a little more about the general types of developers, films and how they work together consider buying a copy of The Film Developing Cookbook. It's a pretty good compilation of information from good sources, and is easy to follow. This might help you decide whether you should stick with what you are using or perhaps go in a different direction.