There is big difference in HP between a 210 and a 212X. The 210 won't carry a boat load of family and do well comparing to the 212X. It will be a good entry level boat however. You can convince yourself that 30mph is all you need, but it won't be, and getting 30 in the wind with a full load will be tough on the less powered engines.
Hull difference is subtle year to year. As far as I can tell, the hull change from past years to those with the articulating keel, have been only changes in lines to add the keel centerline to back to the articulating keel. And plenty of guys have added the aftermarket fins to their boats to make up for the lack of authority the keel system has. The best thing the keel system has IMO, is the rack and pinion steering assist.
Noise reductions has been ongoing. The newer the boat, the less noise...but none are quiet, not even the 2017. It is just quieter than the previous years. The issue is that the engines are higher revving than their I/O counterparts. It can also be said that these jet boats have motorcycle style engines and they are just louder than a V-8/V-6 style automobile engine. And then the I/O vs jet boat is where the last comparison comes in. An I/O has the exhaust below the water level, and it stays below even on plane, whereas a jet boats exhaust is underwater to a certain degree at sub planing speeds but is on top of the water when you plane out. Making the boat quieter has been a goal of many a modifier, and complaint, so Yamaha has been hard at work to reduce the noise. My stereo wouldn't work this last trip out, so I was really surprised how loud it was! We don't typically run WOT, and cruise at best cruise, around 8.5 GPH, which is around 30 MPH. But run around 50 MPH at WOT burning 23.5 GPH. We are headed on a trip that we will run almost exclusively at WOT for 4 or 5 days, covering vast distances on Lake Powell. And fuel economy is less important to me than time to get there. So I was testing running my local lake at WOT, with a broken head unit for the stereo...and that was loud even with ear protection.
Finally, there is a vast difference between the wake board style 212X and the AR210. I am not a tower guy and we don't do wake sports or even ski much anymore. The bigger and easier to use bimini on the SX model boats is much more to my liking. But I would love the tower to put up better lighting. Bottom line, it is a choice you have to make, and there is not a perfect boat that does everything. They are all a compromise based on criteria that is important to you. So enjoy the search and good luck!