Having owed/own both the VTX1800 & Stratoliner S.
Maintaince on the Yamaha is more difficult than the others, but not hard by any means. The Yamaha feels much more refined and balanced than the VTX 1800, plus it has a tach, gas gauge, hardbags, backrest, windscreen, lots more chrome...
The down side with the Yamaha, unless you get a deal, the MSRP of the Stratoliner S is over the top, almost 17K - you might as well by the HD Road king...
As for power both are great, I will say the stock Stratoliner has a nice deep exhaust tone, not loud, but a pleasing sound. I'm getting much more MPG with the Strato than the VTX ever got, even though it’s a slightly larger engine. I am sure many people here may think the air (oil) cooled engine could be a concern, but it’s not, runs wonderful and the heat it puts off isn’t much more than the VTX. As for ride and handling, the Strato has a big edge, I will say the linked brakes on the VTX are superior, and Yamaha at this price should have had ABS. The X has ton of aftermarket goodies, where Yamaha is very limited.
It's easy to see why the VTX1800 was discontinued, I wonder how long the Strato/Roadliner will be around?