How attached are you to those two phones you mentioned. If you are only choosing between the two, then by all means go for Defy
Here is recommendation. This should satisfy your requirements plus more:
Sony Ericsson Xperia Mini ST15i
Price - 13,139
Buy Sony Ericsson Xperia Mini ST15i - PreOrder at Best Price in India - Also find Specifications, Photos, Features & Reviews
Specs -
Sony Ericsson Xperia mini - Full phone specifications
Sony Ericsson Xperia Mini Pro SK17i
Price - 15,799
Buy Sony Ericsson Xperia Mini Pro SK17i at Best Price in India - Also find Specifications, Photos, Features & Reviews
Specs -
Sony Ericsson Xperia mini pro - Full phone specifications
These two phones are of similar hardware. Only major difference is the presence of Qwerty keypad on the Mini Pro SK17i and also the inclusion of secondary camera for video calling.
Advantages -
1) 3 inch reality LED backlit LCD display. The display of this size, the battery should be good than other 4 inch phones
2) Android 2.3 Gingerbread out of the box which is not available in Defy. Galaxy Ace has 2.3 support.
3) This phone absolutely beats the Defy and Ace with the hardware of second generation scorpion processor and Adrenos 205 GPU. So it can play games better than Defy or Ace. Even faster for other functions
4) Music Quality is always going to be good with Sony
5) 5 MP Camera with LED Flash. Sony knows how to make a decent camera. Next to Nokia, I trust Sony for camera in Mobiles
6) Front facing camera. Find me a phone in 13k range to have a front facing camera.
7) Find an phone in 13k-15k range with excellent led backlit bravia display, very powerful processor, dual camera (FOR PRO) and to top it off it comes from an reliable manufacturer is not possible.
Disadvantages
1) While battery life would be better with screen display of this size, I personally find it a bit smaller for extended browing or watching movies/playing games.
2) So other than screen size, for the price it is hard to find any disadvantage for this phone considering it is from Sony.