I have tried all sorts of mechanics in my system over the years.

Dice + modifier. Roll over. Roll under. Dice pool. Variable dice size. Different numbers and shapes of dice for all of the above.

I have always found that d20 + modifier vs. difficulty is by far the easiest to use for a multitude of reasons.

At this point my system uses a single d20+modifier mechanic for everything and is far more unified than D&D which still uses a different system for a lot of mechanics (for example damage and HP generation).

After over a decade of trying, I simply find it works better than anything else.