"corporate companies look for money and large numbers of staff. Web development agencies on the other hand look for quality, code is poetry."

This is a very naive statement. Web dev agencies are looking for the same thing as corporations: to make money, and maintain size or preferably grow. They are just smaller and earlier in the business lifecycle, which means less bureaucracy. Many cater to larger corporations anyway, and face the same political challenges by proxy.

The bottom line is that work experience will depend on your team much more than your company. There are just as many tight knit and creative groups who their love code poetry at big companies as at small.