GPS for Bus Drivers


I currently have a NUVI-660, which is a great unit, and I bought a NUVI-765t, which is not so great, it stays lost more then I do. What id like to know from all you GPS pros is what is the best GPS for Charter bus drivers. It has to work well in large cities and hopefully keep me off restricted streets and away from low bridges. It seems that the two I own both have problems when I am around very tall buildings like in NYC or DC, the 765t just spins in circles lol.. I like Garmin I have has four of there units over time.. But there Unit for trucks is very expensive, soooooooooo any help would be wonderful.....