This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
Prithiraj, The choice should depend on what form of key data you have. If is a number, use the numeric type. Otherwise, use the varchar type. Both are suitable. If you want an auto-incrementable key, numeric is preferred.
For speed, both can perform well since the primary key will be indexed.