Ventajas
Tech One recruits contractors to work for their client companies. Tech One will help prepare you for the initial interview with the client and with whatever logistics are necessary prior to starting work like getting an ID badge. After that, your only real contact with Tech One is turning in your time sheet and getting a check. Otherwise it is like you are working for the client company.
Desventajas
Once your contact is over with the client, you are no longer working for Tech One. Like I said above, it is like you are working for the client company. All your contacts are with the client company. If they decide to hire you full time, great. Otherwise, you are back to square one with Tech One.