I presume the taxi leaves immediately, whereas the wait for the bus might be up to 2 hours. Then the taxi should go straight to your hotel.

If I were going to Pattaya directly after my 12 hour long haul flight, it would be the taxi every time. However, I actually go to Bangkok after the 12 hour flight.

If I have just taken a short haul flight prior to going to Pattaya, then as long as we're not eating into gogo bar time, the bus is a perfectly good option, which I use.