Deltek ERP vs SAP ERP comparison

Deltek is kind of more a niche, SMB player - or at least the situations where I've come across it are companies that are moderately within the mid-market. Most of these companies, if they continue to grow will opt for more mainstream ERP, and if they grow large enough, Tier One packages such as Oracle and SAP. A mid step along the way is into near-Tier One, things like Dynamics Finance & Operation, NetSuite, or one of the larger Infor offerings - as well as a few others depending on industry specific requirements. It's not that Deltek is necessarily bad, it's just hard to compete for smaller ERP providers. Deltek sold in 2016 for something like $2.8b. NetSuite sold the following year for $9.3b and now has a nearly $200b Oracle behind it, pouring development money like crazy into the product. And when you talk about Oracle, It's Cloud Fusion, JD Edwards, PeopleSoft, NetSuite and a couple dozen related products. It's just hard for a single, $3b company to compete with all that. But Deltek is very good within their niche and smaller size companies. So yes, it is normal for growing companies to come off any mid-market offering to Tier One software, which would include SAP. 

Deltek is focused on Project Based Manufacturing and Projects organisations while project management is not SAP's strongest module, and not at the level of reach and depth of functionality that Deltek offers.  I am sure that many may decide to move from Deltek to SAP but would not necessarily be an improvement and probably be a lot more costly