If the total capacity is the same e.g a 2s2p 2000 mah pack (1000 mah cells) vs. a 2000 mah 2s1p pack, it is better to use the 2s1p pack because bigger cells tend to perform better at high C ratings than smaller cells. Also the chance of getting a bad cell is reduced by 50%.
Check out my custom converted 8ight:
Sub 7lb, lowest CG of any 1/8 buggy