One good factor when deciding between two advisors (who are good fits for you personally) is what sort of connections they have. Not necessarily with regards to networking to get you a position after you finish (though that is not a bad thing per se though one must question it to a certain extent as it could keep the old boys network going) but rather when planning experiments. My current advisor (Wise, Kind, Rambling One, W.K. RO) knows practically everyone*. It is invaluable. You have a question, the advisor knows an expert who is friendly & directs you to said person.
My current projects require knowledge of bacteria for which I have not worked with before. For one, I need to know if an experiment has been done before. It is simple to do. Searches through the traditional places have not turned up anything. That doesn't mean it hasn't been done but published in a long forgotten journal. I informed W.K. RO, who immediately thinks of someone he/she knows who has expertise with the organism & contacts said person. It appears the experiment has not been done but the contact will do some more digging. As an added benefit the contact has already made suggestions on the project that will make my life easier. My other project requires fairly complex molecular genetics to develop the strains I need. W.K. RO has me contact the world's expert doing genetic manipulations with this bacteria after laying the groundwork for me. The exchange I have had with this expert has moved and developed the project in ways I hadn't even thought of before we started, setting me up in better position. The net effect should be better publications with less work. Life is too short to bang your head doing experiments that aren't going to be effective in answering the questions you are asking.
This is only a small taste of what help my PI is able to find for us in the lab. The reason my current advisor, W.K. RO, is able to do this is because he/she likes to collaborate and is nice, helping out other professors when she/he can. It is the Golden Rule in action. Not to mention W. K. RO is confident enough to say he/she doesn't now something and ask for help. They are simple concepts to understand & carry out but it amazes me how many faculty members burn bridges & can be egotistically pigheaded. Sometimes I wish a number of scientists would go back to Kindergarten because they missed some essentials from that grade.