You end up at roughly the same point coming at it from either direction. The way you suggested being slightly more expensive in the end for the same effect (assuming you already own a current gen android phone already of course, if not, go with a dedicated screen).
Your way, the resolution is capped at 1200x800 (roughly the same as the Occulus DK1).
With the android rift setup you end up having to lower the resolution quite a bit to get a playable framerate but at least the pixel density is still higher.
Either way works, neither is quite as good as a DK2.
If anyone ever finds a MIPI to anything bridge board (electronics) THAT's the way to go. Buy a replacement panel for an LG 3G (1440p), run it through the MIPI bridge board and let it be driven by displayport/hdmi/dvi/vga. There's currently no consumer grade electronics that can drive a smartphones (MIPI) display though and no displays with a high enough resolution, small enough, that can be interfaced with a computer.
It's either:
Too low res
Too big
MIPI so can't be plugged into a computer
Android rift so too laggy
All of which make it "not quite a rift" even if you can get the tracking right.
The ONLY exception so far is the Nvidia Shield tablet which is 1920x1080p. You can clone your display to the tablet with the limelight driver built into "Nvidia experience" software and the tegra tablets have a hardware decode path that can render limelight in full 1080p with 4ms latency. The shield though costs more than a DK2 so there's no point
personally I'm using Trinus in fake3d mode on a galaxy S5. It does me well enough for now. Will pick up a CV1 when they come out or whatever becomes available once they start open beta testing in April.