In this post I like to highlight a SIP Trunk Provider Evaluation by the Eastern Management Group. I came across a nice article regarding the evaluation of (some) SIP Trunk Providers which was carried out by the Eastern Management Group.
In this study 29 SIP Trunk Providers were evaluated based on a survey. More than 3.000 IT managers were asked. As far as I could read the focus resides primarily on SIP Trunk Providers in the US and such with global reach.

Conclusion, opinion and summary
In case your are about to plan your migration from ISDN to ALL-IP/SIP Trunks or you are considering to consolidate your SIP Trunk connectivity this study might provide you some insights and metrics to get to a decision on which SIP Trunk (Provider) to choose.
However, 29 SIP Trunk Providers are just a few. Depending on where you need a SIP Trunk you might need to research which are available at a certain world region, country and local area. As always on the market there are small and large SIP Trunk providers offering a different feature set for the SIP Trunk Services.
I recommend to take a closer look to what’s offered in detail and what SIP Trunk “architectures” are serviced, e.g. dedicated (physical) link vs. logical link (via existing Internet/MPLS connectivity), encrypted traffic support, clip no screening support, SBC support/compatibility (are there recommended SBCs/IP-PBX by the respective provider?), call authentication/authorization requirements…