There is not a whole lot of info to go off of, but I'd say in general, that a move to a smaller development shop is a good one, given the circumstances you describe. You will get a greater breadth of experience plus have potentially more oportunity to take on greater responsiblity if you want it.
These experiences alone, no doubt, will give you a lot of fodder at your next interview. Moving through various sized companies is not at all uncommon.
You will probably enjoy it more, and given that your resume will show that you have the abililty to work at various sized companies, I'd say it would be a plus.
In regards to "The big question". 95% of your future employment comes from 1) How you handle yourself in an interview, and 2) Who you know, which is how you get your foot in the door most of the time.
If moving to your smaller company makes you think that the 2nd point may be lacking, then you can join other parts of the community such as user groups, conferences, etc. Which you should be doing anyway regardless of the size of your company.
But again, having worked at very small companies, medium companies, and large corporations, I don't believe that the size makes any kind of difference to a resume, and having a broad experience is very eye opening in general. Good luck if you choose to take the job!