is.... Would it be of any benefit to me trying to get a helicopter pilot
job having also become rated in fixed wing? Am I a more attractive
applicant? Or are the two mutually exclusive?

Pretty much the latter. And if you go back to the costs, then there is
no doubt that exclusively helicopter time will be "cheaper".
To get a helo job, you need helo hours. That's what insurance asks for -
usually nobody is interested in your fixed wing hours.

Of course you could get your helicopter commercial with only 50 hours in
helicopters and the remaining 100 in something else. But first you
probably won't be good enough to pass the checkride and second you need
200 hours in helicopters anyway to get your first job which is going to
be instructing. Maybe even 300 hours (common insurance requirement).

So, if you are not interested in fixed wing, go with helicopter hours
wherever possible. Don't even use flight simulators - you need the real
hours. Save your money for the real hours, don't waste it for simulator,
fixed wing... IF you are serious about it. But try fixed wing also
(intro flight)!