Ajax vs DIY systems

Good afternoon. Here I'd like to discuss the main pros and cons of professional and DIY security systems. I will share the information I found and will be very thankful if you criticize it. So, now I am in a search of the best variant of a home security system. I have check different professional variants. Ajax is my favorite one now. I like the variety of devices the company produces, its design, and customer service. The prices are good, but you have to pay for the installers. They do not produce cameras, so you have to buy them from other brands and connect them to the system. As for DIY, you need to install it by yourself and they usually do not have a support line and a long period of warranty. What is better: DIY or pro version?