Noise. Reduce the noise. Built in systems are generally much, much quieter.
For the life of me, I don’t know why portable generators have the same mufflers as lawn mowers, or whey large mufflers are not an after market option.
I’ve thought about making an adapter for my portable, but I worry about messing up the back pressure.
Most portable gens are the high RPM type so you have that noise to deal with also. A low rpm unit like an Onan that you find in motor homes make a lot less racket.
Why not just add a larger muffler after the system?
Make an adaptor, get some flex exhaust pipe and a car muffler.
I once used a 5kw generator, powered by a 10 horse Tecumseh, for my shop.
It ran every thing I needed to run and did so at at time that I could not afford to have a line dropped, etc, etc.
The noise was getting to me, though, even with it outside and the door closed.
I had the bright idea to run black pipe out about 20 feet and put the noise way away from me.
It worked, as far as the actual exhaust noise, but I never realized how damned noisy an engine and generator were if the exhaust noise (the bang) was completely gone.
I mean clanking and banging and rattling and sounding as if it were going to grenade at any second.
Without the totality of the noise (the sound of the whole cycle of suck, squeeze, bang, blow), it was extremely irritating and I just could not deal with it.
It hastened my efforts to get a circuit box in and a line dropped by the power company.