I think your dog is much safer in a kennel. It is attended at least 12 hours a day and many are 24 hour. A pet sitter will stop into your house, feed and perhaps walk your dog and then be gone and your dog is alone until the next visit. If the dog becomes ill or barks or gets into any sort of difficulty, it is on its own. There is also the risk of the dog escaping and the list goes on.
I would suggest you visit kennels in your area, talk to the owners and tell them you will be a regular customer because of your traveling. Have a look at the area where the dogs are kept, they should be indoor outdoor runs, heated and air conditioned if you live in a hot area. It should smell clean, the outdoor portion should be covered with chain link on top of the runs.
Your dog is truly safer in a kennel. That said, if you can find a retired person or couple to move into your house while you are gone, that is probably the ideal. I personally would never leave my dogs at home alone with someone just checking in now and then.
Can you guess, I have been in the kennel business and known a lot of pet sitters, in both cases, some very good and some very bad!