Of the three consoles, only the PS3 is region free in terms of games i.e. you can buy games in the US or in Ireland and they will work. This is NOT the case in respect of Xbox 360 or Wii. (Although some games for XBox may be region free depending on the publisher).
The only slight downside to buying a PS3 in the USA is that it is region locked for Blu-Ray movies.
The NTSC/PAL thing isn't an issue with modern TV's.