I cannot complain as a Katy stan. Huge singles, pretty good album sales, all around improvement everytime she starts a new era, consistency, longevity, willing to promote her album for multiple years.
For Nelly it's by far the TSI era, everything drove me crazy. Despite it being a high quality album, everything went wrong when it came to promotion and singles choice etc. They literally didn't do anything right, apart from maybe the UK promo when Big Hoops was released. Hence it being a top 15 hit there even though it flopped everywhere else. WFTN reached top 10 in Russia on its own out of nowhere so there was clearly hit potential. Didn't even get the slighest bit of exposure on iTunes when the album dropped, an absolutely useless pushback of 3 months, Bucket List supposedly being released to iTunes in Germany etc on March 9th yet it never appeared there. Big Hoops adds date on US pop radio shuffled around too much, and that was also the only adds date Nelly got for pop radio that entire era. The following two "US singles" were hardly promoted nor were they sent to pop radio. I can go on FOREVER, it's an endless list of ****-ups.