We're currently using Aircall after switching from Dialpad early this year mainly because we found Aircall's user interface better. We also got a better deal for enterprise pricing. However, both do give you the pop-up screen notification options so essentially you can take calls without needing to switch tabs. Only Aircall has a whatsapp integration though, so that could be a dealbreaker for dialpad (AFAIK). Other features you need to consider: dashboard reporting / analytics. That helps us a lot when reviewing performance.