Just putting my 2 cents in it.
If you already have a SAP ECC which is oriented towards your production process , the SAP CRM solution would help you more. You could reuse the master data through middleware ( after some custom coding) obviously and run the sales process in SAP CRM. So sales & service processes could be run smoothly. Marketing in SAP CRM sucks I would say and you would need to buy a TREX or HANA possibly to segment large customers. This is an additional cost overhead.
If you have consumed the SAP ECC and there is lesser customization , then it makes more sense to go for SalesForce solution.Also UI wise there is no comparison. Salesforce beats SAP CRM handsdown.
Also one of my personal observation for the growth of Salesforce is that the developer community has the access to Salesforce study material and unlike SAP no knowledge is locked in service market ( little would be a better word actually)place or sap notes for which you need to have a user id and password. Also its certification policy are geographically neutral and one can easily go for a certification without needing a go ahead from respective companies ( At least in India SAP certifications are that way) So adoption becomes that much easier for a company thinking of migrating to SAP CRM or any solution. Now try doing the same for SAP hybris and you would need to provide your company TAN no for getting a quote for training. So even if you want your employees to scale up either become a SAP partner or SAP consumer. You cannot test waters just without being either one of them. .It means that it easier to scale your employees in Salesforce than in SAP CRM any day. I see so many Salesforce companies which have mushroomed in India and so many big companies who have moved from Siebel to Salesforce so effortlessly and have been easily able to scale up their employees in 3 months at a minimal cost.