If you ask 10 people for their opinion on most things, you are bound to get 10 different answers.
Keep in mind everyones needs, when it comes to VoIP providers, will be different. Your location will play a big par on which provider you ultimately choose, but where you call the most will be a big factor.
Do you want local trunks, with a second provider for domestic and international long distance? Will the company that probides local service be able to match long distance rates with a provider that specialises in that? Do you want pay per minute long distance, or something close to a flat monthly rate? What are the billing increments?
What about ISP failures? Will the provider forward calls to another number if your local power fails, or your ISP connection goes down? Do you want DID service, or simple in/out trunks?
Lots of questions to ask potential providers so do your homework. Get some suggestions, then ask questions before deciding. And you generally do get what you pay for, so don't go on price alone. Sometimes a higher price for access to quality support and service, is worth it.