I am waiting for delivery of new irons this week - scheduled to arrive tomorrow. I'm also playing a round Friday at Spanish Bay (Monterey, CA) with a group of guys I haven't played with in a long time and am really hoping to play well (last time we played I was probably a 40 cap). If the irons arrive in time would you play them or would you wait until you've had a chance to play a few rounds and dial them in? I could see where jumping onto a challenging course with brand new irons fresh out of the box might be a disaster. On the other hand I can hardly stand to look at my old irons since hitting the new ones at the store...
Tough question!!!! I guess you can't put off the game? Just kidding, mostly.
Only your gut can answer the question. Here are a few things to consider perhaps.
How different are the new clubs from the old ones? Are the new ones more "players" clubs that are likely to be less forgiving of slight mishits due to unfamiliarity? Are the lofts different so you may be unsure which club to use from given distances? Are the swing weights different so they will just feel "different" when you hit the course?
Those are all reasons to play with your old sticks. A lot of this could be mitigated if you have an opportunity to spend some quality warm-up time on the range without pooping yourself out for the actual game. Or it could confirm that you need to leave the newcomers in the trunk for the day.
Go have fun, and don't second guess the choice once you get going!
When it comes to new equipment I am like a kid at Xmas. Waiting to find out if I like it isn't an option for me. I keep grips, tape and solvent in my desk and have been known to sneak out for a quick 9 after buying something new.