I would say that whether local or virtual business coaching is better is completely dependent on the person. I offer both, and most of my clients take advantage of virtual coaching because they are in different parts of the country or in different countries.
There are many fantastic online business coaches. My recommendation would be to take advantage of the free first session (for those coaches that offer it) to make sure the two of you can work together.
Certifications are important. The International Coach Federation is the gold standard of coaching today, but many colleges are now offering degrees in coaching as well. I would recommend taking the college path because you learn a lot more than just coaching, and many colleges offer certification as part of the degree.
The number 1 thing to look for in a business coach is compatibility. Hopefully the coach you are considering has a free initial session so you can make sure that person is good fit with your personality. An amazing coach may not be the right one for you if your personalities clash.