The HC-110 developer is indeed different. You're likely to be able to get more intensity in the highlights, and a coarser grain along with quite a bit less shadow detail. Some of that can be brought back by tweaking development with the Xtol, but you're right, they will not look the same, especially since Xtol has so much shadow detail. You can, of course, underexpose your negatives somewhat to get a similar response. And you can gain most of the highlight intensity by agitating more often and develop longer.
Cardwell was the one that turned me onto replenished Xtol, after a venture with Edwal 12. Edwal 12 is another interesting developer that is fantastic replenished, but I have a feeling the grain will be too fine for you if you like HC-110. You might want to check out Edwal 10. You have to mix it yourself, and it looks pretty much just like Edwal 12, but it doesn't have the super fine grain. It's wonderful replenished and gives an S-shaped curve with a bit compressed shadows and highlights. But the highlights are soaringly beautiful with amazing modulation right at the edge of blocking up.
Xtol, to me, is just the best compromise. I can do almost anything with that developer, I can shape how the negative prints by altering my agitation cycles and development time, mostly depending on what I want and what the lighting conditions were. So, sometimes I might not be able to get the very best highlight intensity, or a firmly S-shaped curve (like Edwal 10 and 12), but I can get close, and I just want one single developer to do everything for me.
You could buy a pack of Xtol and try it, of course. It's very economical as replenished.
- Thomas