Hi, there are various types of Blackberries available in the market. So it solely depends on how you are going to use it. Usually blackberry prospective buyers expect the following features from their blackberry: Push Email, BB Messenger, Internet Browsing. They usually do not expect it to be media powerhouse since it has decent specs but albeit lower compared to Android or iOS. So please let us know how your dad will use the blackberry.
1) Blackberry Curve 3G (9300)
Price - Rs 13499
This blackberry model is capable of HSDPA and also has WiFi b/g/n. Hardware wise it is decent and capable of handling decent tasks. CPU rated at 528 MHz and RAM at 256 MB, internet browsing and multitasking can be done with less strain. Good screen resolution and size at 2.46 inches. But it has inferior camera at 2 MP and would not be recommended for photo shooting. Maybe capable of taking occasional snaps. Also is capable of document editing and viewing.
Specs -
BlackBerry Curve 3G 9300 - Full phone specifications
2) Blackberry Bold 3 (9780)
Priced at Rs 21,299 this model seems to be the best choice Blackberry has currently available. It has excellent 624 MHz processor coupled with 512 MB RAM which is more than enough for handling tasks that the blackberry requires. Given the OS, this hardware will give you a pleasant experience. It has a decent screen size of 2.44 inches which is capable of 65K colors and gives a nice visual experience. The Bold series has the best keypad layout than other Blackberry models and also has touch sensitive trackpad. It also has an decent capable camera of 5 MP with LED Flash which is more than sufficient for photos. All this plus legendary Blackberry experience. I would absolutely recommend this if your budget is in the 15-20k range.
Specs -
BlackBerry Bold 9780 - Full phone specifications
2A) Blackberry Bold 2 (9700)
Priced similarly as Bold 3 at 21,594, I would not recommend this above Bold 3. Now this has same processor as the Bold 3 and is predecessor of Bold 3. It has lesser RAM of 256MB and also comes with Blackberry OS 5.0. The 3.15 MP camera is also lower in standards compared to Bold 3. So while it is recommended above other models, I still think it is not better than Bold 3. So you might well as buy Bold 3 when looking at Bold 2 given the price difference.
Specs -
BlackBerry Bold 9700 - Full phone specifications
3) Blackberry Curve 8520
Price - Rs 8989
This phone is excellently priced for customers who wants Blackberry that can be used for emails, documents editing and also internet browsing on the go. It seems to have decent specs and also should handle basic functions with ease. But it has lower resolution screen and inferior camera. IT DOES NOT HAVE 3G.
Specs -
BlackBerry Curve 8520 - Full phone specifications
4) Blackberry Torch
Price - Rs 26854
Torch is overpriced and it is not different from Bold 3 except screen size and touch screen with pull down keypad. My recommendation is check the price. If you can get Torch for cheap than BB Bold 3, then by all means get it. Else you will still be happy with Bold 3, if you decide to buy it
Specs -
BlackBerry Torch 9800 - Full phone specifications
5) There are other models like Storm, Storm2 etc but Storm does not have WiFi while Storm2 touch screen experience is not good. So if you are buying a Blackberry for your dad, it is better to buy one with keypad as that is what made Blackberry a Blackberry.
So given the price range, you should set your sights on Bold 3. It will give the best experience for your dad. But at the end, it is yours and your dad's choice. So choose what you like and suits your requirements.