We used Dupont StoneTech since it was recommended by where we bought our travertine tile from. I have also seen lots of good reviews on it.

Whichever one that you get, try it first on some samples of your stone. Then test out the sample to see if water beads on it and if things like red wine will stain it. If that goes well, then apply to your counters.

Dry-Treat makes quality sealers. Aquamix,Miracle,Fila,Lithofin,Dupont,and many other sealer companies make quality products. Yes many fabricators and refinishers have their favorites that they are comfortable using.
Sealers are composed of resins which are carried into the material to be sealed with a water based or solvent carrier.
Solvent carriers are generally better penetrating than water based carriers as water molecules are larger. However some water based sealers can be very effective sealers.
The best products will be oleophobic and hydrophobic meaning they will resist oil and water based staining.
The most important issue about sealing in my opinion is testing and understanding the surface you want to seal.
Testing porousity can be done by leaving a palm sized puddle of water on the surface for 10-15 minutes then wipe away and see if a darker mark has remained. This will tell you the surface is porous and can be sealed. If you dont get any absorbtion then you will have to consider your surface may not need sealer. The material could be very dense and will not absorb much of anything. It is possible the stone has been resined at the processing point and will take little or no sealer at all.
If you do need to seal think of the process as applications.
The water test has given you an indication of how porous the stone is. I dont think in the term of coats of sealer but think applications would be a better description.
Another words when you start the sealing process on a porous stone your first application can be 2-4 coats done in manageble sections so that you can be sure all the excess sealer has been removed from the surface. If you notice on the first coats the surface darkens and the sealer is being absorbed thats good. On that forst application you can load up the stone with sealer then make sure all the residue or left over sealer is totally removed. The surface should feel dry and a paper towel wipe across the surface should come up dry as well. Then wait 24 hours and do the water test again. You will see a difference in the absortion in most cases but id you do have absorbtion than repaet the application until you no longer have absortion.
The reason we wait 24 hours is that most sealer take from 24 to 48 hours(or even longer) to cure.(resins to harden in the pores of the stone).
The list of performances for a sealer is as follows.
Sealers will temporarily inhibit the intrusion of staining agents. With this in mind remember that daily maintenance of the surfaces is very important.Also sealer swill wear from harsh chemicals. Using PH neutral cleaners will maintain the life of the sealer.

Sincere thanks, srosen, from a granite newbie.

Dupont StoneTech was recommended by our fabricator.

This site sells a variety of good-quality sealers. I've personally used the Akemi Nano on their recommendation for marble with very good results, both on kitchen counters and in our shower.

But they sell other good sealers and I found their technical info to be reliable.

Here is a link that might be useful: Tri Point