Pirep:

We flew into Linden, New Jersey, LDJ.

It was about 45 minutes into the city by taxi ($100) and about the
same total journey time back by train and taxi ($much less).

The airport was great. It's quiet and small so time spent taxiing was
minimal and time spent waiting for other aircraft was zero. The staff
at the FBO were very friendly and helpful, and the first night's fee
of $20 was waived with fuel purchase. I really liked it.

I've never flown into the big ones, but my guess is the extra time you
spend taxiing and queueing eats up the time savings of being closer
and much of the cost savings of being closer if you take a taxi.

The biggest disadvantage was the trains don't go that often so you
could have to wait.

Overall a great experience though.