1.5 vs 1.6 roller rocker ?'s

[cornutz]

Can someone explain the major diff's between the two...

You see, I want to put a nice mild roller motor in the burb, and I would like to know what the deal is with the two... they seem to be very close, ie: one tenth off right? Also, why do some people on flea bay have sets for sale that have half 1.5 and half 1.6 ratio... Do they use one for the intake and one for the exhaust? and why do that?

Anyway, like I said I want to put in a hyd. roller cam, rocker, lifter setup into the balanced block that I have on an engine stand in the the garage, but I have never tried this route...any help would be appreciated, Thanks.