Airport Transfer Dubai & Bangkok

[pakora]

Hi all, me and the wife going to Dubai for the 1st time and wanted to know is it cheaper to book transfer to hotel before hand or to just get a taxi, and would it be the same for Bangkok. Is there any public transport options - metro in Bangkok and Dubai Metro, does anyone have any experience.

Going on the 25/01 to Dubai staying at the Hilton Dubai Jumeirah.
Getting to Bangkok on the 30/01 and staying at the Shangri-La Hotel

Thanks for looking.