You get what you pay for.
Pay 10 grand to the likes of Dialogic, and get the royal treatment with a contract SLA that they follow to the letter.
Buy a Dell, get some Joe who gets paid jack and really doesn't give a damn about your problem further than maintaining job security.
Ultimately it amounts to how much the tech is paid. Have a company with well paid techs? They will probably do anything for you, and can solve most of any problem (or they will quickly be replaced).
Low paid techs? They are probably more interested in doing their own thing for improving their skills to make them attractive to other, higher paying employers, rather than focusing on things that will resolve your specific issue with a specific vendor's technology.