Which one is the best for a IT Company, hiring a professional web developer or outsourcing to a professional web development company?
Very strange question for a seemingly successful IT company to be asking, you’re in a better position than most to answer this 
I’ve absolutely no idea which is best, so i’ll just throw out a wild speculation.
If you hire a web developer (which you already have a few) - they’ll know whats going on in the code two years from now.
Two contractors down the line - they’ll be charging you for learning the code before they even alter a single line.