Poodles don't shed, but need daily brushing (if not hourly...)
Labs shed, but brushing isn't necessary except on a weekly basis (although daily is recommended).
Poodles can be trained to fetch, same for labs, except labs tend to look like they have more fun doing it.
Poodle hair is a PAIN to brush and to get stickers out of...
Labs and poodles are equally hyper for the first 3 years. After 3 years, the labs tend to calm down, the poodles stay hyper.
Grooming a poodle (cutting) can get expensive if you are not the one doing the clipping.
I prefer labs because they seem to want to please the owner a bit more. Poodles are smart, but a bit...well, stuck up if you will. They want it to be their idea to do something whereas a lab will do it no matter whose idea it was.
As for service work:
The poodle may be the best for it as it wouldn't cause many issues with allergies.
The hair of a poodle may get in the way of the eyes and cause the "goop" to stain, which may be a turn off for some people.
Labs immediately look friendly. I think it's in the eyes and the blockier face.
Both are good breeds but you will generally see mixed labs or even pure labs in the shelters that would make excellent therapy dogs or hunting dogs if given the chance...good luck deciding!