I've been doing the same research here as well. High level summary of what I've found:
- Concept 2 - seems to be the workhorse of rowers and is a standby in gyms and what many competitive rowers use. It's also not terribly expensive. Doesn't really use the big video displays that Ergatta, Hydro, NordicTrack and others are using. This is more like a cyclometer, if you've done road biking. It tracks pace, distance, watts, etc. but it's a no frills data screen.
The high enders - Hydrow (Magnetic resistance), Ergatta (Water), & Water Rower (err, water)
Hydrow - is the Peloton of rowing, s e xy design, quiet, lots of bells and whistles and the video screen rowing led by an instructor. $3k to get in the game and then the monthly subscription fees.
Ergatta - the Gamers approach to rowing. More soothing due to the swishing of actual water (requires treatment tabs every so often so there is some maintenance), additionally, the resistance is increased or decreased by the volume of water in the tank(i.e. you need to drain water if you want to decrease resistance. Might not be the best option if you have multiple people of different strength using the rower). Stylish, made from quality wood. Consistent complaint I've read about - foot holds are oddly close together and can be weird when your are compressed at the bottom of the rowing cycle. Using game theory with its screen so you are constantly pushed to achieve new levels and personal bests but it doesn't offer the guided instruction that Hydrow does. From what I've read it's not a pro/con issue on the screen presentation but a personal preference. pricetag - similar to Hydrow
Water Rower - parent of the Ergatta. High-end water rowers.
NordicTrack - Gets high marks for using magnetic and air resistance. follows similar instructor led video.
Hydraulic cylinder rowers - honestly, I haven't looked at them. They are way more cost effective.
I've watched a lot of youtube review videos, but have, frankly, been too cheap to make the plunge.
From what I've read, most of the higher end rowers are all 6-8 week wait periods for delivery.