What are your thoughts on unified mechanics versus varied mechanics? For example, pre-3rd edition D&D had a mix of methods for determining dice results: roll over, roll under, d20 for combat & saves, d100 for thief skills, d6 or d10 for surprise, etc... while 3rd edition and onward all use the d20 roll-over mechanic for everything. Do you have a preference? Or does it matter at all? Perhaps your preference is determined by the style of game you're looking for?