buying a windows now is not practical,unless you are going to die tomorrow and cant wait to use a windows device.
windows 8 device are coming soon so wait.
blackberry is only good for BBM and its keypad.
Android is your only option now .
and among those droids,
1.Xperia U.
2.Neo V/Ray.
3.HTC desire C(underpowered but smooth)
Why is buying a WP7 device impractical? You still get the 7.8 update + it is not going to loose app support as WP8 devices are going to be at least around 20k price bracket. So new WP7 devices will still be launched.
Xperia U is impractical because of 4 gb memory.
Neo L is out of budget
In my opinion Omnia w is the best device in this budget.
You get 1.4 ghz processor, Super Amoled screen, 8 gb memory and the super smooth WP7 OS.
OP just give a WP device a try, you will love it.
For this budget Omnia W is the best.
*www.saholic.com/mobile-phones/samsung-omnia-w-i8350-1002466