what is the difrance between the two?  The same magazine the same lenght barrel.  can anyone help?
GL

The P228 is an older model SIG, based on the larger P226.  It's available only in 9mm and is somewhat hard to get since SIG isn't importing many nowadays.  They seem to have moved on to the P229 and a new version of the P226.  Basically, the P228 has a rolled and welded slide with a pinned in breech component (firing pin, extractor, et al) where the P229 is one piece of stainless steel that has been milled (to much higher tolerances).  This allows the slide to fire 9mm, .40SW and 357SIG without trouble.  However, if you buy a 9mm P229, you can only fire 9mm in it.  If you get the .40/357SIG P229, you can retrofit it to 9mm.  The frame on the 9mm only accepts the thinner 9mm mags.

All that said;
If you want a great compact 9mm, go with the P228.  It's lighter and very reliable.

If you want a more sturdy compact capable of other calibers, get a .40SW P229 and get 9mm or 357SIG barrels from BarSto.

I loved my two tone p228...regretably I sold it during my lean years...Lite and accurate.

1) You can not convert a 229 from .40 to 9mm.  The case of a .40 is larger and the extractor will not work.  .357 sig and .40 s+w are based on the same case, so converting caliber can be done by switching barrels.

2) I have found that 228 mags and 229 mags are "interchangeable" in a pinch.  I asked a factory rep about it and he said it "was not recommended."  I can find no differences between the two, except markings and placement of the little holes in the back for round counting.  Feed lips appear identical and mags have functioned flawlessly when tried.

Conversion of the .40W/357SIG to 9mm is well documented.  It's easily done with a Bar-Sto barrel.  Call them.