A few things were not mentioned which I feel need to be.
Using a pet sitter does have it's issues as does a boarding kennel. There are dogs who can tolerate one but not the other. If your dog has behavioral issues, and you are not confident in the knowledge and training of your pet sitter ( which you should) then you are best to leave the dog at a kennel where there will be minimal interactions. Usually a petsitter who believes a dog to be questionable will do several trial runs before a person goes away to be sure that in the person's absence the dog will not misbehave in a way that is unhanldleable (ie. not letting sitter in the door). I have never once had a dog not let me in the door....but, it is a possiblility.
As for a fear that neighbors, robbers, whatever will observe a sitter coming and going... You bet! Because of the higher expense of a petsitter, there are often very well off people who use the service. They WANT someone coming into the home 3-5x per day. It is a crime deterrant. Having lights turned on at different times during the day, shades pulled up and down, driveways plowed and pathways shoveled lets a potential burglar know that someone is either home or looking after the place. On top of that, neighbors generally keep an extra close eye on the house too! A pit fall could be if the pet sitter had a vehicle with business magnets adourning it! I go incognito in my jeep..... Nothing lets that person know I am not the home owner... I would highly discourage anyone using a pet sitter let thier sitter use magnets or signs on thier car while they are parked in thier driveways.
Some animals clearly need more attention then a sitter can give them. Others actually get more from the sitter then they do from thier owners. We have clients who NEVER walk thier dogs on leashes... Imagine how exciting it is to these dogs to enjoy life past thier yards!!
Yes. Screen both. Fortunately there are alot of petsitters who take thier profession very seriously, they come educated in the animal field, continue thier education, regularly compete/train with thier animals, and constantly seek more information to gain skills in many facets of animal care. You'll see retired veterinary technicians, CPDT's, Animal Science graduates among a group of professional petsitters. You'll also see people who "love animals".... As a professional who has a degree in animal science, who competes/ trains her animals, continues my education, and is passionate about my field (hubby works along side me with similar credentials). I ask you to do your research. A true professional petsitter will be just that, professional. They will greet you with a client contract, they will be insured, educated, they will belong to national organizations and follow thier code of ethics. They will treat you and your animals as clients, and respect you as such.
All of the best. I have worked in boarding kennels, and have seen good things and bad things..... The ABKA (
www.abka.com) should have a listing of member kennels. Tour the facility, smell it, notice food/ water bowls, are they clean, are the animals clean, do they look happy? How is the staff? Ask for references ect.
Good luck. Either way, if you do your homework, I suspect you'll be pleased.