SATA and IDE are just the types of HDD connectors for HDD drives...
IDE are old ones:
http://thumbs.dreamstime.com/z/black...tor-332017.jpg
SATA are new ones:
http://www.sierra-cables.com/Cables/...al-Cable-1.jpg
So you should get SATA drives...
If any provider still offers IDE HDD-s - avoid them at any cost since they are renting rather old servers...
Performance of HDD is often neglected but it's very important since it's the bottleneck of the today's servers (until we go fully SSD)