My standard developer is Ilfotec HC, and formerly Kodak HC-110, which is near identical.
Before that, I used D-76, and then ID-11.
Both are good. I like HC better because it is more convenient, more consistent, more contrasty, and I always get near 100% use out of the bottle.
I think I remember figuring out one time that at dilution B, it is actually not cheaper than D-76 1:1. This is assuming 100% usage of the D-76.
I will go through the math again to make sure.
HC-110, dilution B (1:31): $14.69 makes four U.S. gallons of working solution, or $0.92 per U.S. quart.
D-76, 1:1: $6.09 makes two U.S. gallons of working solution, or $0.76 per U.S. quart.
Ilfotec HC, 1:31: $38.99 makes 32 L of working solution, or $1.22 per liter.
ID-11, 1:1: $10.99 makes 10 L of working solution, or $1.10 per liter.
So, Kodak D-76 is the most economical developer, assuming 100% usage.
Additionally, if you use raw chemicals, you can easily make D-76 much cheaper, while the formula for HC is not published.
You can also use higher dilutions of any of these developers.
For some reason, Freestyle lists the 16 oz. HC-110 as making two gallons. This is a mistake due to lack of clarity. It does not do this unless you are using dilution A. It makes 1/2 gallon of stock solution. 1/2 gallon of stock solution mixed 1:7 into dilution B makes four gallons of working solution.
Here is what Freestyle has to say about HC-110 (same as Ilfotec HC):
"Fine grain, sharp working formula supplied as syrupy liquid concentrate. Good enough for Ansel Adams! Kodak HC-110 is a liquid-concentrate film developer introduced around 1965 and widely used ever since, particularly in photojournalism and fine-art photography.HC-110's selling points are ease of use, versatility, and reliability. The concentrate keeps for years; it's easy to mix up enough developer for one roll at a time; all types of black-and-white film can be developed with HC-110; and results are consistent. Compared to D-76, this chart indicates that HC-110 (dilution B) produces: Slightly less shadow detail or true film speed; Slightly finer grain; Slightly lower acutance. Where HC-110 really shines is in scientific work or push-processing, where film is deliberately overdeveloped to increase contrast and speed. HC-110 gives surprisingly little fog even with very prolonged development."
...and about D-76 (same as ID-11):
"For general use
Yields full emulsion speed and good shadow detail with normal contrast
Moderately fine grain, excellent development latitude
Replenish with KODAK PROFESSIONAL Replenisher D-76R
For normal or push processing
Powder"