Brushed 19T Motor

[dibble34]

I have searched for this info, but struggled to find anything.(i am rubbish at searching though ) I have a ZX5 with a 4.5t brushless that is stupidly fast , but i also have a ZX5 RTR with a stock 20 Turn motor in it that i use what the track is damp/greasy as the othe car is a nightmare in those conditions. My question is would i notice much of a difference if i replaced the stock 20t motor with a 19t and what would people suggest? I don't want to spend too much so looking for some ideas for things i could get off ebay second hand etc

Cheers

Dave