I just replaced my Jabsco with a Raritan Sea Era
I suggest that you compare the outline drawings and hose positions of both toilets before starting the installation. My install took me about 4 hours because I am slow. In my case the 1.5" waste hose to the holding tank needed to be shortened and the intake hose for the seawater needed to be lengthened. Knowing what hose you need in advance will make the job go smoother.
I went with the seawater flush model. I understand the advantages of fresh water flushing but I just couldn't justify the use of the fresh water. I had figured that I would use about 20+ gallons every 4 days for my wife and myself, but I am finding that the Sea Era flushes with less water- I can't quantify the usage yet, but it could be as low as 60% of the manual usage. So maybe the fresh water option is not so bad.
The mounting holes for the Sea Era don't match the Jabsco, but I plugged the exposed holes with plastic plugs that I bought at the hardware store.
My first plan was to mount the intake water strainer inside of my sink cabinet but it did not fit very well. In retrospect the external mounting will be much easier to service and really doesn't look that bad.
We have used the toilet for a couple outings and are happy with the performance. A guest tried to flush a heavy personal wipe and the maserator in the toilet would not process it. Clearing that clog was very easy- the item was reachable with a long-nose pliers and easily extracted. No dis-assembly required. Your mileage may vary.
Below are a couple of before and after pictures-