Voxeo has a much more complex, full-blow VoiceXML language, the setup is more complex - you have to tune things, and overall the complexity of making calls is higher. They were also much more expensive at the time. It started at 12 cents per minute in the smallest bucket, which is highway robbery.
Although they were launching their own version of an offering similar to Twilio in response to the competition, it may be out by now? They also have a pretty liberal development account policy, that lets you do a good deal of testing for free. They also bill at half minute intervals, which I don't think Twilio does... which can make 30 second calls with them cheaper, even if you're paying 7 cents a minute (at a higher volume bucket).
If you need full blown VoiceXML, Voxeo is good. For most people, Twilio is quite good enough - and lacks the enterprise XML baggage.
Disclosure, before I start, I run Voxeo's Developer Network.
We think there's room in the world for both API-based cloud options and XML standards-based development. We have a variety of options for building and deploying apps and a wide range of pricing. From 3 cents per minute in the cloud to enterprise apps with SLAs that run the voice applications for some of the world's largest companies.
For our enterprise customers, many of them prefer to use the w3c standard VoiceXML to avoid vendor lock-in. Some of them also use our proprietary CallXML, a simplified language for building apps. These apps run on our carrier-grade hosting facilities in the US and Europe or at the customer's data centers.
For web devlopers, we have Tropo.com, a cloud service offers APIs for popular web programming languages. Build in PHP, JavaScript, Ruby, Groovy, or Python, with more options coming shortly. Pay as you go, develop in your native language, and run your apps in a cloud on top of the same infrastructure our enterprise hosting customers use.
It's more than voice. Using one code base, your app can not only make and receive phone calls, but also send and receive SMS messages and interact over IM and Twitter.
As rjurney mentioned, we're developer friendly. You can create an account on either Tropo or on our enterprise hosting for free and run there as long as you need to without charge. We don't put any artificial limits on our dev platforms. We'll give you a dedicated phone number for your app. We'll also give you Skype numbers, SIP addresses, an XMPP address, and a toll-free number. Build and test your app, hand it to your friends to try out. When you're ready to move to production, let us know.
Tropo is the new offering I was talking about, and at 3 cents a minute that is a pretty compelling offering. Bravo. I should also add that Voxeo technical support was some of the best I've ever dealt with. It could be 2am and the night guy would respond immediately, and I got through to engineering promptly if necessary.
I see now that Twilio is also now 3 cents per minute. Neck and neck :) Both offerings look pretty good.
Although they were launching their own version of an offering similar to Twilio in response to the competition, it may be out by now? They also have a pretty liberal development account policy, that lets you do a good deal of testing for free. They also bill at half minute intervals, which I don't think Twilio does... which can make 30 second calls with them cheaper, even if you're paying 7 cents a minute (at a higher volume bucket).
If you need full blown VoiceXML, Voxeo is good. For most people, Twilio is quite good enough - and lacks the enterprise XML baggage.