Travelling from SBC (Bangalore) falls in RL (Remote Location) quota. But if you book it from KGI (Kengeri) it would be GN quota. Njoy confirmed tickets. And you can board at SBC since they are only 12 kms apart.
even though KGI is GN quota it has only 2.5 coaches under GN quota and SBC being in RL has 4 coaches. Half coach is for HO and tatkal. Cancellation from Bangalore are more hence chances of confirming is more in RLWL in this particular train
Also extra coach is generally attached to this train (S7) at Bangalore only and forms part of Bangalore quota only- also more chances of cancellation are from Bangalore- so if availability is there book from KGI- or else from SBC only
Now Change of Boarding Station is allowed since 1st October 2013.
How does this affect your suggestion.
you can change the boarding point at the PRS as well, if you didn't do at the time of booking.
cancellations are very less here sir. This is the only decent night train between SBC and TPTY