Is there a difference? I just got into a 1 year contract with orkin and must say after one application to my basement and perimeter of house, I haven't seen any bugs. I had some sort of infestation of sow bugs which of course brought in spiders. Their spray worked well but if I bought a spray at a big box store could I expect the same results? I hate being in a 1 yr contract but I was desperate.
I have had both services and DIY over many years and houses. I HATE bugs, ants, or other creepy crawlers in my house. I have always had better results with a service than DIY. While more money, I pay for the service.