For your information, here are two another new comparison tools.
The first is dedicated to SMS rates (by VoIP operators).
Link:
SMS-Rates.Com
The second is dedicated to VoIP rates for major popular operators as Skype, Wengo, Betamax network (Voipbuster, Netappel et cie),...
Link:
VoIP-Rates.Net
They are managed by
VoIPfr.Org, a french-speaking portal about Voice Over IP which also edits a similar comparison tool.
NB: In order to avoid to switch manually between SIP accounts, you can use a PABX (provider can be associated to a country, for example). I also discover an online SIP switch:
MySipSwitch ("
set up customisable routing and dial plans to as many different SIP providers as you need").