Hi,
Congratulations on your decision! Sounds like you have a great background for it.
Speedy soft is a "fill and print" software, not a practice management system. It is a lot cheaper but it has a lot less capabilities. For a billing service you really need a practice management system. You need to be able to post payments, print patient statements, run aging and other reports, etc.
As for the 2 you mentioned I am not familiar with either. We use Lytec. But what you want to make sure of is can you do multiple providers, can you eventually have more than one computer hooked up to the same software (Lytec has limits depending on the version you buy) what types of reports does it run, do they have regular updates, how does the tech support work. These are some of the important things to consider. Make a chart showing the two softwares. I'm assuming they are comparable in cost to each other. See what things they both offer, that should help you pick.
Choosing a PM system is one of the most important decisions you will make. You need to choose wisely.
Good luck
Michele