A couple of things to note, the biggest is usually not the best, so one who sells the most, may not be the best agent. You want an agent who knows your area, knows your neighborhood and can provide the services you desire. you want to find out what they charge and what you get for what you will pay. you need to know how much they advertise or market, do they complete their own showings, will they be there after a sale for inspections, appraisal etc? and how will they communicate and how often to you.
Lastly you should not look for prices using a price per square foot method for residential homes, there are too many factors that affect it such as age, if it has a garage, how many bedrooms, baths, finished basement, upgrades like a fireplace, granite, hardwood, a pool or the lot size. You really need to look at the house as a whole and compare to the 3 most recent solds and 3 currently for sale and adjust for differences.