As a Buyer Specialist, I get interviewed all the time. Not everyone goes with me nor do I want to work with every buyer I come across. Though there are variables such as personality that may affect your decision (as well as the agent's decision), I strongly believe that the following things are very important for you as the buyer to consider and review:
1) The number of buyer (NOT seller) transactions the agent has had within the last 12 months in the area(s) you are considering buying in.
2) If looking at new construction, the number of new homes the agent has sold within the last 12 months.
3) The sales price to list price difference/percentage (including seller concessions and other terms) of the last 12 transactions the agent has facilitated to see what their negotiating skills are like.
4) References from the last 3 to 5 buyer clients the agent has worked with.
5) Their online presence and invlovement within the real estate industry (e.g. "google" their name for results, check for them on Trulia and other sites to see what their responses have been to real estate related questions/topics, etc).
6) Check with the Virginia DPOR to see if there are any complaints or actions against the agent - http://www.dpor.virginia.gov/dporweb/dpormainwelcome.cfm
7) Ask them how many properties they preview per week on average. This will indicate whether they are staying on top of the local inventory and market trends. If they don't preview, they can't be up to date.
8) How well do they communicate with you and how do they go about doing that? Do they respond quickly and with accuracy and knowledge?
9) Did they ask you what your specific needs are in detail? This indicates that they care about what your needs are and don't just want to throw you in any house that may pay them higher commission or is one of their or their friends' listings.
As for bringing them to the same house, you can do that. But you are playing with fire - if you ratify and offer on that house, the other two agents could argue that they had procuring cause and could go after you for the commission. I don't necessarily agree with that argument, but everyone feels differently and there are plenty of lawyers in the area.