I currenty own both of the pistols in question. I have a DA only P226 (not a DAK) and a DA/SA P229 two tone. Both feel similar but of course the P226 is a little larger in the grip length and barrel length giving it a bit better balance. Now when looking into a used Sig, please be aware that there have been changes in the general design. Older, West German marked Sigs, usually have a carbon steel folded slides and have all required German proof marks. Sometime in the mid 90s parts were shipped from Germany to the US for final assembly and do not have the proof marks as required by German law. Than when Sig Sauer North American came into being, all production started to shift to the New Hamshpire factory and slides started to be all milled units. There also was a shift from internal extractor to external extractor. So please do some research and be aware of what you are buying and what you are paying for, especially for a used Sig. I will say, SIGs become a addiction once you have one, but you will almost always never own just one!
Good luck and happy shooting.
Oh, the P6/P225 would definitely be a great start to any SIG collection. Love mine, well love all of mine...lol