The difference is ... Presto itself could never use more than one core on a multicore processor. If you have a quad core system, Opera 11 itself never uses more than 25% (and possibly another process for plugins). I'm not sure you can even find a current system with a single core processor. But also, if one process gets hung up everything else will continue to work. But there is overhead involved - both in RAM and speed - with multiple processes as well, and if you were running on a single core processor Presto would blast Blink "out of the water".