Yes, that's pretty much true about the Jewel/Gem comparison... plus, Jewel doesn't have a bowling alley.
In the name of full disclosure, I have toured N. Jewel, and have not been on N. Gem. That said, I felt that N. Jewel was stunning. NCL did a great job with this class of ship, IMO, based on my tour of N. Jewel and our cruise on sister ship N. Jade. I'll now let others who have been onboard Jewel for more than a few hours have their say...