question on using hybrid turbos (diff in/ex sizes)

[tastyratz]

hello, would someone educate me on this? i always see all different kinds of turbos and sizes. i see people using t3/t4s, etc. and all different wheels. what is the benefit for using a larger exhaust wheel? if you wanted power why wouldnt you just run a much smaller sized ex. wheel and a big giant intake wheel? wouldnt that spool better, produce much less heat from much lower shaft speed, etc.? why do they only vary so much and what determines the level of variance?