In the documentation of mining pool I found following

Connect Details:

(Difficulty 5 - GPU) stratum+tcp://stratum.btcprivate.org:3032

(Difficulty 10 - GPU Farm) stratum+tcp://stratum.btcprivate.org:3036

(Difficulty 15 - Nicehash) stratum+tcp://stratum.btcprivate.org:3096

I see that only differents between difficulty. I have a farm of 6 card which connection should I use and why?

Any ideas? Thanks!