IPT has a terrible reputation. Apparently the tracker was known for DOS'ing other trackers. Your POV on FL is odd becuase IPT very much feels like a pay to leech site with many ads or promotions asking for money. Also with FL you have to be able to use Bitcoin so only small % of members will use that to buffer their acc...
I would take a FL proof any day over IPT. I also dont care about amount uploaded, its more important to see users seed times which can easily be verfied.
And as mentioned before, IPT is sometimes refused as a proof in the filesharing community so not worth using as a primary account if you have limited bandwidth or have ambitions to advance quickly in the private tracker hierarchy!