I have to say neither. Both usually lead to remorse and consequences even if it is just anxiety over an STD.
Depends what you're after. If you want someone who'll do what you want and with absolutely no commitment or any fallout, go with an escort (...just make sure s/he uses protection; if s/he doesn't insist on a condom, in fact, steer well clear). Meeting someone online is always risky; their intentions and their situation aren't clear - whatever they say about themselves, you can't be sure there's no ulterior motive or that what they say is true.
If you meet someone online, you can't be sure of their perceptions. To you, three short emails may be a perfunctory courtesy prior to meaningless sex... but to them, it might imply the start of a relationship. The last thing you need is to meet someone for sex, and have them turn bunny-boiler on you.
If this is related to your other question, though, frankly I'd have to say that neither is OK unless you've discussed it and you've given your EXPRESS permission. If this is not the case then you're talking to the wrong people - you need to go and have a frank conversation with him. It's not OK unless you BOTH think it's OK; you have the right to ask what's going on, expect the truth and - if you're not happy with it - to categorically demand that it stops. If it doesn't, it might be time to get out.
NO... go get to know someone and find a relationship..get tested with a new partner, and feel free to have sex....but dont risk your health for one hour that will fade...and then you go looking for more..learn to be loved forever not just for a moment...