The snappy answer is, you need both. Large enterprises with diverse needs fundamentally need a complete CRM application with a versatile toolkit and solid platform. But not everyone is a large enterprise, and even in the enterprise there may be good reasons to have separate CRM instances — for example, in Corporate Development or HR.
Your choices have become more complicated, as the CRM vendors have OEM relationships with vendors who sell highly tailored vertical solutions built on top of the cloud platform. While these solutions add a lot of value with features, these OEM products are far less flexible than the vanilla CRM application. Sometimes the OEM's added value may actually limit the utility of the original platform features.
So here are some guidelines for decision making. Note, in this article I am using Salesforce.com's third-party apps as the examples only because I know that marketplace better, not because I'm trying to hawk or criticize any particular product.
If what you really want is just a set of stand-alone features, OEM products are often a terrific value. OEMs strip away some of the standard features of the salesforce CRM system, replacing them with their own functionality. If the OEM has done a good job, their feature set is going to be a much closer match to your needs than a "vanilla" CRM system. If they've done a really good job, the UI has been streamlined and a lot of clutter has been removed, which speeds user adoption. Best of all, the OEM product may sell for the same price as the full-featured (enterprise) version of the vanilla CRM system.
Sounds like a pretty sweet deal, but there are some issues:
• Some parts of the product will be in code you can't get to, and some of the pages will not be customizable through the administrative GUI. Customization of OEM products is likely to be more expensive than with the vanilla CRM system.
• The product you are buying is sold and supported only by the OEM, and you will not have access to Salesforce.com's support.
• If the vendor goes out of business, sells off the product, or simply discontinues it, it's not at all clear how long their product will continue to work. The cloud offers no magic here: make sure to negotiate hard on this issue before you sign up.
• The OEM product is typically a new instance of Salesforce, so if you already have a Salesforce instance you'll have to migrate the relevant users and data off your existing system. This is anything but free.