Radeon HD 8750M 384 @ 620 - 775MHz 128 Bit @ 2000 - 4500MHz
that's the same chip as the R7 250.
but you have to know exactly the version you have, since the 8750M DDR3 is much slower than the GDDR5 version... anyway, I would expect the 8750M GDDR5 to be maybe 15-30% slower than the 7730 GDDR5, and the 8750M DDR3 to be slower than the 7750 DDR3
7730 have 384sps/24TMus just like the 8750m BUT higher clock and 16ROPs compared to 8 from the 8750M/R5 250.
so the 8750M GDDR5 is slower than the 6670 GDDR5, but probably faster than the 6670 DDR3.