I've recently got to shoot the 228 and I will say it's a great pistol. I can see where it gets people really into them being they are a little lighter (mostly due to slide design) and that lends itself t a little better balance. If I was to be looking for a carry 9mm then it would be on the short list and probably be the topper.
Thing is I don't like to carry a 9mm all that much. I carried 1911's for years so that meant the 45 ACP was the only round to have. As I got older I stared looking at other pistols and did buy a P226 9mm mainly for range fun. I had shot a P220 before that. That was what me looking at Sig Sauer. I got the chance to get a 229 a little while back and I thought it would make a good carry pistol. I'm still a 1911 guy through and through. The design has proven itself far too long to say that it is inferior. But Sig Sauer have shown time and again that a "modern" combat weapon has a place in the LEO and civilian sector and they will live up to the moniker "To Hell and Back Reliability".
what keeps me from wanting the 228 is the fact that it's a 9mm and I just don't care for the round as much as a carry option. It's a good round and it will get the job done no question. It's just not for me in that capacity. I do like it as a range round and I use them often when I'm out shooting. For me the biggest selling point for the 229 is the fact that with that beefier slide you can shoot the .40 but can switch over to a 357 Sig round and there is no question that the weapon will be able to handle it without any lingering feelings about it causing any damage over time on a lighter slide. and it's nothing to switch again and make it a 9mm to lower ones ammo cost at least for practice.
So for me the 229 wins over all for me as an all around more versatile weapon. Now if I was more of a 9mm shooter I would lean to the 228 being it's in the caliber that I would be looking at and it's over all a better feeling weapon if a 9mm is what you are looking for and not the other two calibers that a 229 can shoot with relative ease.
If you want a good 9mm run with the 228. If the heavier loads are your cup of tea then the 229 simply offers more opportunities it seems to me anyway.