You are correct in your observation, about the only difference I can think of is the 'full service' carriers tend to have better schedules, and the appetite to get you on your way again if you're flight is cancelled or connection missed.
Other than that you might as well go with the cheapest option as a cookie and wifi is not worth the cost.
I also question the difference between business and economy these days beyond the larger seat.
I mean, is a toasted sandwich and glass of wine worth the extra cost?