After my initial comments, above, I decided to do a slightly more controlled test of Firelite and Esbit tabs.
Set up: 12 ounces of cold tap water in my Snow Peak 700; the Firelite Ti stove; and an aluminum windscreen of the proper size. Using HALF of a fuel tab, test how long it takes to boil 12 oz of water, and how long the fuel remains lit. (I chose 12 ounces b/c that's the most common amount that I need for a freezer bag meal or coffee.)
Conditions: On my deck, temps 30-F, no wind.
Test: I burned 1/2 a Firelite tab, then cleaned the stove, cooled the pot, refilled it, and repeated the test with 1/2 an Esbit tab.
Half Firelite Tab: boiled 12 oz of water in 9 minutes, burned out after about 12 minutes. Left pool of sludge in bottom of stove.
Half Esbit Tab: Burned out after 12 minutes without ever bringing the water to a boil. There were small bubbles forming rapidly on the bottom of the pot, and some steam when I removed the lid, but it was not boiling. There was no residue of any sort left in the stove.
Conclusions: The Firelite does indeed have more heat energy than the Esbit in this test. The only downside is the sludge left in the stove, which is somewhat difficult to remove even in my kitchen sink.
For my style of backcountry cooking, I normally want to boil 12 ounces of water twice, one for my meal and one for a hot drink (e.g., oatmeal and coffee in the morning, freezer bag dinner and decaf hot tea at night). Under good conditions (no wind), the Firelite will let me do this with one tab per meal, which is great.
Finally, a word on cost. I bought 12 Esbit tabs at my local outfitter this afternoon, at a total cost of $8.01 with tax, which is the same per-tablet price as the Firelite tabs including shipping from BPL. I know I've seen the Esbit tabs for a lower price locally, but even so, given these results, it would be a false economy.
Now, if anyone could suggest what to do about that sludge, I'm all ears.