I've been on NCL Getaway and Escape few years back. Love the dining choices and service from crew was always excellent. Staterooms are nicely appointed. Entertainment is good. Enjoyed Legally Blonde (broadway musical) and comedians. Pools are very small, but luckily I was able to secure access to vibe beach club on both sailings- which requires you to rush to ship and be first aboard to get in line for access. Did not enjoy that rush, but think Vibe is essential to enjoying time on deck as the pool areas are way too crowded. Spice H20 at back seems ok, but just a water feature no pool. In Vibe (still no pool, just water feature and hot tubs), you got amazing service from bar staff, and was able to make friends from other people in Vibe throughout the week.
I did feel like NCL was cheaper than RCCL when they combine the perks, vs booking on RCCL and buying drink/ dining packages separately. This is why went back to NCL a second time, pricing overall won.
I've been on some older RCCL ships, so not a fair comparison to NCL's newest, but I think the lines are far more similar than different, and if you enjoy one you'll enjoy the other.
One thing RCCL excels at is in their ship design, and wow spaces which push the entire industry forward. I'm excited to finally try an Oasis class on Harmony in a few months. As one who appreciates interesting architecture and design, RCCL (and Celebrity) have no peers. NCL builds nice ships, but they seem like nice public rooms built into the generic box ship, vs as as RCCL's ships seem designed especially for the grand spaces Think ten deck atriums, three and four deck dining rooms, expansive mall like multi deck promenades, and Central Park and Boardwalk built into the widest hull with a split superstructure of several decks cabins above. It is really amazing how they designed the Oasis Class, which has still has no peer in the industry over ten years later.