First of all, private transport from SG to Genting.. its at least $350-380 per trip, round trip probably $700.
You need to have at least 7 people to be economic, as most coach bus is around $80-100/pax, plus the need to take grab transport to pickup point.
It is more of a convenience if you had elderly and young.
The private transport will allow FOC 2 pickup point at your residence, additional need to pay extra.
As for comfort, not much, the gap between seats is smaller in a private transport for a headcount of 7, lesser headcount, you probably had more space, at the expense of affordability.
You should tried Transtar Club Z or Solitaire, it is much more spaceous.
I had taken private transport twice, there is no much time saving, as you likely to arrive about the same time as coach bus. I would rather take coach bus.. the queuing issue resolved once you had applied malaysian MDAC..
The e-gate gantry clearing in KSAB is faster than the SG's autogate.