After much discussion and advice last year, I decided to go with a separate ATS (automatic transfer switch), even though my Prosine has a built-in transfer switch with the inverter.
I like this for multiple reasons, one of which is not limiting my shore power load to the amperage of the inverter unit.
I can easily use a smallish or largish inverter and with the 30amp ATS I have...get full 30 amps when plugged into shore power or the generator.
I also like the ability to fully control the inverter state, though I've not had experience with using the in-built version ;)
That being said, I'd agree with the above advice- separate components. Might even find a more frugal unit whose pricing went into "inverter components" instead of ATS components ;)