I haven't seen a full comparison of all the coins, but I haven't heard of any altcoin advertising slower or more expensive than Bitcoin. Whether its IOTA or one of the other better known alts you don't have to look too hard to find cheaper and faster. Bitcoin like the apple iPhone was revolutionary but competitors gained ground and when they are better/faster/cheaper then market leadership changes at least for the transaction space. Bitcoin has far more trust than anything else and perhaps that is enough to hang onto the reserve title. As you say there are always trade offs. Bitcoin is trusted because of its established architecture and the use of resource intensive mining but that comes at a cost that can be optimized but not removed. Tinkering with the code to make incremental improvements may undermine the one true advantage Bitcoin has ie trust but is unlikely to beat the rising competitors on speed or cost. I like and own precious metals. Gold and silver coins are more practical than bars but I still dont use them for buying stuff.