Choose a spreadsheet if
you sell on one or two channels in one country and your catalogue is under a few hundred SKUs. A spreadsheet is still cheaper and faster — until it isn't. The moment that changes is usually the second country, not the second thousand SKUs.
Choose a feed manager if
your product data is already correct somewhere else and your problem is getting it out in the right shape. A feed tool does that well. It does not hold the canonical record, it does not know your stock, and it will not treat a missing EPR number as a reason to stop.
Choose a PIM if
your problem is enrichment and governance across a large catalogue, and selling operations are somebody else's system. A PIM is built for the catalogue; it is not built for what happens after a listing goes live.
Choose Zuduno if
the same products go out to several channels in several countries, the rules differ per market, and the catalogue, the stock and the orders currently disagree with each other. That is the case this is built for, and below it something simpler is the better answer.