I know this question makes me look like an idiot, but what is the difference. I own a 229, I know it comes in .357, .40, and 9mm, and that the 228 is only 9mm but are there any big differences. They look really similar. Just something thats been bugging me for a while.

Main difference is the 229 slide is machined steel whereas the 228 slide is stamped steel.. The 228 slide weighs less, but the 229 slide should be considerably stonger.

The 228's have a stamped slide which is actually made in two pieces and then welded together. The slides for 229's are made from a single piece of steel, which, as I recall is actually blackened stainless steel.

I think the 229 was designed around the 40 and so it is built a little stronger for that cartridge..
Current 229's also have a stainless slide..not sure if they have always had a SS slide.

I just sold my 229 and bought a 228.  I've also heard that the 229 was designed around the .40 and the 228 was designed for the 9mm.  This makes sense because the slide of the 229 is quite a bit larger (fatter).  The 229 was actually a bit more difficult to carry than because of the fat slide than any other gun I have and I had a VM2 for it.  Not that it was that hard to carry/conceal, but it's fat for a compact.  I decided to go 9mm and 45 only so I sold the 229 and got the 228 which I want for a shoulder holster.  The 228 has a significantly slimmer profile than the 229.  

I would get a 228 if you want 9mm, the 229 if you want 40.  

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The 229 can be bought with a rail when the american 228 does not.  There suppossed to be a 228R that is only sold in europe. There are a lot of rumors now about the 228 being discontinued or being sold only to the military.  They are both great guns.  

That's true.  The 228 will no longer be available because Sig doesn't want to get them from Germany anymore, as opposed to making them here in the states.  So if you want one you better act fast becausw they will not be around long.

I have been hearing the "228 is going away" rumors for at least 10 years, and yet they are still here.

I agree with everything in MokeyGrip's post, especially the last line.  There really isn't any good reason to get the 229 in 9mm, it's just bigger and, I believe, heavier.