The most important is that they offer free support, also all their services are very well priced (at least compared with others).
If you use other companies like HP or Cisco - it's not easy for them if there will be any problems in future when using those products/services from us because we have full liability over our systems! I think this would make sense only where security issues can occur without having access control rights etc., but normally these kinds things should work just fine even by admin users alone so no need extra costs here unless something goes wrong which happens rarely enough anyway :).