Hosted VoIP vs. None Hosted

Hello,

Currently my company is looking to replace our old PBX system with a VoIP service. We got quotes from two different companies.

Company A will provide a Hosted VoIP which will install a T1 line to our address with a Cisco router with patch panel for our calling lines. Also, they will provide the Mitel 5224 or 5340 phones.

Company B will install a T1 line, a Cisco router, and a Mitel 5000 system on our site along with Mitel 5224 or 5340 phones.

The cost per month is $400 less for Company A than Company B.

Anyone has expericne with Hosted VoIP in terms voice/call quality...etc?