How does this compare with Twilio on cost and deliverability?
Provider based on price depends on how heavily you use US vs World, and if it's SMS (and/or MMS needed) or Voice or both and what volume you are operating at. For pure SMS with a balanced mix of domestic and international, I would probably suggest AWS Pinpoint at this point. Their international rates compared to Twilio are fantastic for all the locations I spot checked.
A lot of people are on plans which let them receive unlimited texts in the USA, which means the provider is absorbing the cost, but it still is much cheaper to send.