If you don't care how it looks, a 10K bulb is going to give you more PAR than a 14K or 20K bulb.
If you are planning to keep tricky anemones like S. gigantea or H. magnifica, I would go with 10K. If you are going to use a 400 watt bulb it doesn't really matter. It starts to matter some with a 250 watt. IMO, it matters a lot with 150 or 175 watt bulbs.