Making the decision to pursue the right sales channel is important, and changing your strategy is only as inflexible as the contracts you sign. Sales channels will directly impact your sales volume, financials, brand image, and customer relationships.
Let's say you've built a new B2B software product and you're trying to acquire your first 20 customers. You want to be as close to these customers as possible so that you can get feedback and iterate on your product. If that's the case, resellers or channel partners probably aren't right for you (yet).
As a B2B company, you should consider that resellers and channel partners can be great ways to accelerate growth, but they likely won't be able to create it from zero. They are very good at selling third party software (why you chose them), but they're incentivized to make money and to have happy customers. If you don't have case studies or social proof, then it makes your product harder to sell because it's an unknown quantity. On top of that, the reseller doesn't want to risk their relationship with a loyal, happy customer on a piece of software that may negatively impact the relationship.
If you're B2B, then consider the case that resellers and channel partners are strategies to accelerate and speed up existing growth, but not to create it
Diversifying across several sales channels may mitigate risk, but "spray and pray" doesn't normally work well when it comes to running a successful business. There is a cost in terms of time and money involved with each choice. As an example, let's think about online marketplaces:
Time: Each marketplaces will require an initial profile to be set up and then potentially maintenance down the road as you update your product details and marketing materials. If you've spread out across ten marketplaces, how often are you updating your product or company information there? Do you have to constantly make updates to make sure you're in the top search results on any given platform? How do you handle customer reviews in each marketplace?
Money: Marketplaces are generally not free and typically they charge the seller. Some are pay to play (i.e., you pay 3% of the list price to the platform only when an item is purchase) or some have a list fee (i.e., $2000/yr to list your software on a platform) or they may do both. A $2000/yr investment to sell your enterprise software on a platform may sound like a deal when compared to the cost of a SaaS sales rep, but if the math is that easy - why aren't all of your competitors doing the same?
ROI: You want to feel confident that the investment into the marketplace is worth it. Can the marketplace sell enough product to generate a positive ROI? In the B2B software space, there are a lot of companies (normally startups) trying to launch the next big platform business. This means that there is a growing number of options in the space and ultimately a lof of these marketplaces will fail to deliver. This is something I've found to be very common in the B2B software space selling into the US Department of Defense (DoD). There are several publicly funded marketplaces as well as some stood up by the DoD with the intent of helping get innovative tech into the government, but unfortunately these marketplaces don't produce results.