Squid90:
So question is would a single cell get drained faster boosted or a 2~3 cell bucked drain quicker. FYI battery capacity will be identical in either situation
If the power consumption is the same for both setup then a single cell will always drain faster than 2 or 3 cells (unless your buck converter is very crappy)
Convert your battery specs into mWhr + consider conversion efficiency and you'll get the idea.
Example
Battery
1 cell = 3.7V*2600mAh = 9.6Whr
3 cell = 3.7V2600mAh3 = 28.8Whr
9.6Whr < 28.8Whr
Efficiency
Boost converter = 90% efficient
Buck converter = 90% efficient
Boost = 9.6Whr*90% = 8.6Whr
Buck = 28.8Whr*90% = 25.9Whr
So we get 8.6Whr < 25.9Whr
Now let's say IF your buck converter is only 25% efficient, THEN
Buck = 28.8Whr*25% = 7.2Whr
So this time - boost 8.6Whr > 7.2Whr buck