Indian Railways runs special trains to accommodate extra passengers during peak season. For this purpose, they have to re-use old/spare coaches, engines, etc. Also, since special trains are not part of the regular rail traffic, they have to wait longer at signals, and allow regular trains to pass.
So, travel in Special trains involves frustration, and is usually uncomfortable. You should use them only as a last resort to get from A to B, if you are not getting tickets in other trains.