GH/s is better.
Hash rate denominations
1 kH/s is 1,000 (one thousand) hashes per second
1 MH/s is 1,000,000 (one million) hashes per second.
1 GH/s is 1,000,000,000 (one billion) hashes per second.
1 TH/s is 1,000,000,000,000 (one trillion) hashes per second.
1 PH/s is 1,000,000,000,000,000 (one quadrillion) hashes per second.
Conversions
1 MH/s = 1,000 kH/s
1 GH/s = 1,000 MH/s = 1,000,000 kH/s
1 TH/s = 1,000 GH/s = 1,000,000 MH/s = 1,000,000,000 kH/s
and so forth
To be totally honest, those usb chips are obsolete unless you use them to learn with. You would be better off getting an antminer U1 which gives you 1.6 to 2.2 gh/s each for around $60 bucks on Amazon.
From what I've read the Antminer S1 is the best bang for your buck right now from Bitmain.