Between digital and physical products, I find it much easier to do the digital ones. Now this is personal to me and it may not be so with you.
I have tried to do physical products, but I've not done so well with these, albeit, I've not particularly given this due diligence yet and am not ouside of doing another physical product campaign.
I particularly like the digital products because you can find those that provide recurring income, especially those with membership sites for which Wealthy Affiliate herself, is a prime example.
Digital products tend to be much less expensive than their physical counterparts, but this isn't always the case.
I have personally become acclimated to digital products, how they are promoted and what to look for in them and their promotions.
The only real maintenance needed on physical products is making sure they are up to date and accurate. Physical products, especially consumer electronics and machinery, are high-maintenance. If you promote used stuff here, the refund rate can get pretty high.
These are just a few reasons. I've given a few pros & cons to digital products...