OK, there really is no better or worse company as to what the policies cover. Plan F from BCBS covers the same as a plan F from Humana, or Colonial Penn or any company that is allowed to sell in your state. The difference between policies will be in what the premium is. Likewise for a plan G, or plan K, or Plan L, or any other plan you choose. Some policies offer a level premium but cost more in the earlier years of their term and some increase a bit as you age. Premiums can also increase as the members of the pool you're in have more claims. If you have a plan with one company and you feel the premiums are getting too high, there is an open period each year where you are allowed to switch plans or companies and not be denied coverage because of any pre-existing conditions.

There are Medigap brokers that can give you details on what is the best fit for you and the state you're in. Premiums will be the same whether you buy through a broker or do it by yourself. Of course, you can also shop brokers so that keeps them pretty honest if they know that you're looking at what another is recommending.