Concerning conversion:
Basically, it will be crazy-crazy...to try and convert HTML back into a domlog...probably not impossible, but not easy...and even it you could extrapolate the data, I'd be willing to bet that it wouldn't contain every-little-detail that was in the original log
Concerning resources:
I'm not sure what kind of resources awstats normally uses. Logaholic can be fairly intense but it's speed reasonable. If you have a LOT of heavy traffic'd sites on the same server, you will likely see some performance issues during domlog processing.
All that said, I think the end result is better: you can make comparisons that aren't possible with the others. Logaholic is being actively developed, so it's likely to only improve, both with interface and usability as well as in the internals of the application and its parsing.
-DavidN
small anecdote...my experience only...you will need to evaluation your own experience:
I was testing a domlog yesterday...it had ~1.5 million entries (512mb file) that took about 25 minutes to process on a idle box; the load went from about .3 to 2.3 over that time period....while that seems outrageous, the same domlog with webalizer did NOT complete within 45 minutes and had similar load.