The assumption that you get the best quality Salesforce Consultant by engaging an Implementation Partner is simply not true.
While there are many benefits to a Partner and plenty of scenarios where this is the correct resource strategy, do not default to the assumption that it is the right approach for every project! Some of the negatives to engaging a Salesforce Partner:
Consulting Partners deliver the work and leave in a hurry
As with any type of outside Agency, their business runs on delivering projects efficiently so they can manage their workload and move on to the next project. 'Scope creep' is a term that terrifies any Consultant - it happens when the requirements change during the course of a project and results in a longer overall project timeline. If you are working with a team of Consultants that need to move on to the next project by a certain time, this becomes a big problem!
It means the end of implementations can be rushed, which sometimes results in low quality user acceptance testing and handoff to the internal team. This can create issues if the documentation isn't perfect and your team doesn't know exactly what was delivered.
All project deliverables will be scoped upfront
In order to achieve the above, the start of an engagement with a Salesforce Partner will involve scoping the entire project from start to finish and solidifying a timeline for when everything is scheduled to be completed. Obviously, project timelines are critical for success; however, it means there is very little room to maneuver. The problem with that rigid approach is that you will often learn new things along the way - your business is evolving, you identify new needs, or you make new discoveries that change the original plan. This makes perfect sense!
But it's difficult to make any changes to the project scope when using an Implementation Partner. After all, those Consultants are lined up for another project when they are done with you and they need to finish the work and move on!
Salesforce Partners want to execute 100% of the work
Perhaps you have a perfectly capable internal Salesforce team - Administrators and Developers that are already on payroll and would, in fact, love to get their hands on this new project. A Consulting Partner isn't looking to give you one of their high-value Technical Architects just to direct your internal team - then they would only get paid for 1 Consultant.
They want to staff an entire team on the project and bill out a team of Consultants. It's simply how their business model works. This means that regardless of what expertise you have within your company, the Partner will be pushing as many of their Consultants as possible, which not only increases the overall cost of the project but also makes knowledge transfer harder during go-live, since your team wasn't doing most of the work along the way.
An Implementation Partner is VERY expensive
The typical hourly rate for a Consultant working at a Consulting Partner is $250/hour to $400/hour depending on their experience. And you are likely engaging an entire TEAM of Consultants. Sure, they will tell you it's because they are the best but it's really because Consulting Partners (and any business for that matter) have a lot of overhead, which needs to accounted for in their price.
Comparatively, Independent Salesforce Consultants charge a significantly lower hourly rate - typically in the range of $100/hour to $175/hour. A Freelance only needs to be paid for their time - they don't have a Marketing team, an Accounting team, or a huge physical office space, so their lack of overhead is a win for you. And don't be fooled - their experience level is identical to the Consultants you get from a Consulting Partner since many Independent Salesforce Consultants used to work for a Partner!
If you hire a Consulting Partner, you interview the company, not the individual Consultant
This is a big one, especially given how difficult it is for Salesforce Consulting Partners to hire top talent. When you go through your vendor selection process with an Implementation Partner, you aren't interviewing their entire Delivery team. You aren't meeting the specific Salesforce Developers or Salesforce Architects that will be assigned your project. You are meeting the Sales team and the company Leadership.
It's all too common for companies to select a Consulting Partner because they were impressed with who they met, only to find inexperienced Consultants assigned to do the work. When partnering with an Independent Salesforce Consultant, you interview the exact person that will do the work and know what you're getting every single day.