Reid had a successful spell at The Hawthorns last season on loan from Blackburn in helping them gain promotion back to the Barclays Premier League at the first attempt.
But he admits the lure of joining Celtic was hard to resist before deciding to make a full-time switch to the Baggies after parting company with Rovers.
Reid said: "I would be lying if I said there wasn't an interest there (from Celtic) and I went up and had a look around. With my Irish connection, there was an affinity with Celtic and it was a big pull.
"Had West Brom not been promoted, that could have made a difference and you want to play in Old Firm games.
"But I weighed everything up, looked at the standard of the two leagues and signing for West Brom was a much better move.
"The Premier League is the best league in the world and I'm glad I've got at least another year at that level."
Reid, 29, is hoping his experience of top-flight football in this country will be beneficial if Albion struggle.
He said: "There are going to be times when it will be difficult and we might go a few games without a win.
"Hopefully I can bring a bit of Premier League experience because it's not going to be plain sailing."