There are a number of good companies out there. My suggestion is..if you're a golfer..talk to your local course greenskeeper. They usually have a couple they use on a regular basis.
Look for a company that will send out a certified "Arborist" to give you an opinion.
I was at one time responsible for 12 acres of turf with 400 trees on it. I hired an Arborist to give advive only, and then hired companies to carry out the work.
The main reason for this is simple. Most tree companies have trucks and employees they need to keep on the raod making money. Some companies will "over quote" the work needed to be done in order to keep the employees busy when often less work is actually needed.
Trimming trees is done for many reasons. Are you looking to esthically imporve the tree or ensure it will grow properly without crossed limbs that eventually will stunt the growth. There's a lot of factors. Also, some trees should be trimmed at certain times of the year than other trees.
I also reccommend that you do not root feed with high Nitrogen content infusions. It potentially damages anchor roots and it creates an artificial enviornment that the tree is living off of. Once the root feeding stops the tree hasn't put out the proper feeding roots to sustain itself and you run into problems.
Never EVER run a weed whacker around the base of a tree to trim the grass. That little line the nylon or wire cord leaves on the trunk is an open invitation to all the creepy crawlies to enter the tree and dmage it even further. Nothing limits the life span of a tree more than trimming damage at the base of the tree.
Like I said..pay for your advice..then contract the work out as needed. You'll often save a lot of money working that way.
This is not to say there aren't some very reputable tree companies in the Metro area...but the more knowledge YOU have the better the whole porcess will be. Start with a local greenskeeper for some ideas and suggestions..
hope that helps