Twilio vs google voice api for SMS [closed]

The API you are linking to is not an official Google API and therefore there is no guarantee that either it will work reliably or that Google will not decide to disable the API at some point. So you are paying for a level of reliability rather than relying on an unofficial hook into Google Voice.

There are lots of SMS APIs available, Twilio is a well known one for sure but there are others.Take a look at another answer I posted a while back listing some of the providers. How to send SMS programatically in a professional and reliable way?

Google Voice appears to limit the number of SMS messages that can be sent. They don't go into detail about the limits.

To prevent abuse, there are limits to the number of text messages you can send from Google Voice. If you've reached the limits, you will see a message that says 'Your message was not sent because the text message limit was reached. Please try again later or try sending to fewer contacts.' You'll have to send to fewer people, or try sending your text message at a later time.

Twillio does also limit the number of SMS messages, but it's a documented limit.

Each Twilio SMS-enabled long code (regular 10 digit number) can send 1 SMS message per-second, per-number. Unfortunately we are not able to adjust this rate limit. If your application requires a high volume of outgoing SMS, we recommend using an SMS short code.

So I guess the difference is, one may cut you off, but is free. The other won't, if you stay with in their limits, but costs money.