I agree with Larry on the flourochemicals being the best sealers and giving the most repellency. Most of the durability issue has to do with how the floor is maintained rather than the sealer applied. Some things they can grab from under the sink to clean day to day will tear up a stripper over time.
The price should reflect the size of the tile also. Smaller tile means more grout lines. This usually means more labor time and more sealer required.