My experience with Dell is that they are not that focused on selling enterprise support (at least compared to HPE), at most they will push for bundling hardware (cables, cable trays, front covers, PERC...) that you do not really need in order to get better volume discount.

Price-wise I don't see a meaningful difference between Dell and SuperMicro (or even "non-traditional" server vendors like Asus and Gigabyte).