I'd get whichever you can find the cheapest. You might be able to talk down the price of a 32 more then a 23.
When I bought my glock they had a 32 and 23 in stock but the had a 23 barrel. I was able to get the 32 plus 23 barrel for the price of the 23. The shop owner was looking to unload both.
I prefer shooting it in the 357 sig configuration however I have no problems with the 40 round.
Last edited by CynicX; Tomorrow at Beer:30