Multiple logs for WWS doesn't matter anymore, they removed the option to include multiple logs with their new version.

I haven't encountered any errors with Recount yet, although I've found that Recount calculates DPS differently than WWS does and I'm not sure which is more accurate.

And what Madox said was absolutely correct, except for me being an expert, about WWS. Just something I want to highlight though. For WWS all you have to do is visit their website, and I think a java file will be downloaded, probably to your desktop or wherever, then you can choose a log to create a report of. You don't really have to 'install' anything, except for an addon to record your combat log.