Overall, I am getting similar framrates with either setup in BF4 and Planetside 2(I play these games the most).
A10-7850K + Gigabyte R7 250 2GB(dual graphics mode)
BF4 50-60fps with some drops into the 40's(medium settings @1920x1080 res)
Planetside 2 40-70fps with some drops into the 30's(medium settings also)
With Powercoler R7 250X 1GB (running discrete no dual graphics)
BF4 45-70 fps never below 45fps
Planetside 2 pretty much the same as running the R7 250 and APU in dual graphics mode.
Been running the APU @4.2Ghz with graphics clock @960Mhz and 1GB system memory shared for the APU paired with the R7 250 in dual graphics mode.
With the R7 250X installed, left all settings for the APU the same even though I cannot run in dual graphics mode.
I like the performance either way, though I do wish I had waited and picked up an R7 265 since they are now on Newegg. (pretty much an R9 270 but with 1024 shaders instead of 1280).