SharePoint 2010 Web Parts and CRM 2011 Online - Middleware WCF Service or WSDL based proxies

Hi,

I need to write some web parts for our public facing on SharePoint 2010 that will use CRM 2011 "Online" as back end. Web parts needs to pull data from CRM Online and write changes back to CRM Online.

CRM SDK requires .NET 4.0 but SharePoint 2010 uses .NET 3.5. My understanding is it leaves with me two options:

1. Create a WCF service using .NET 4 that become middleware between my SharePoint solution and CRM. My webparts will call my WCF service that in turn would talk to CRM.

2. Use WSDL based proxies to talk to CRM Online directly

Which one is the better approach? If I go with second approach, what do I loose that CRM SDK offers? 

Thanks,

D.