I'm not sure why you're saying it's cheaper. As Danielle mentioned, the prices are actually very less. And as a developer, every penny difference counts. Also they give $30 credit, which is more than enough to "try and play" and release your app to production.

I agree with point "3" though. I use Twilio for an app which sends voice call reminders to other people. But when automatic reminder call goes to these people, it goes from a 1-877 number and many people don't pick up the phone thinking that it's a spam number. Instead if I could call from the number of an original user who sets the reminder, that would be really great.

Point "6" also seem to be great, and I'm sure Twilio will add that.

But somehow, the article coming from Tropo's evangelist is not strong enough or convincing to make a switch from Twilio to Tropo. In fact you did a good job in highlighting some of the technical differences. I think the post lacks these kinds of specifics.