Piece by piece earns more. One lot is faster. Everything else follows from how you value your own time.
The honest numbers
Singly reaches the person who wants that one thing, and that person pays the most. But it is thirty listings, thirty descriptions, thirty parcels, and months.
As one lot reaches dealers and people who like a gamble. They will bid, and they will bid at a level that leaves them room — because they are taking on the work you declined.
The gap between the two is roughly the value of the work. That is not a trick; it is what the work is worth.
The split most people should use
Neither, exactly. Sell the good pieces singly and the remainder as a lot.
A collection is almost never uniform. Three or four items carry most of the value, and a long tail carries the rest. Listing the tail individually is weeks of work for very little, and bundling the good pieces throws away the money.
So: pull out the pieces that deserve their own listing, run those properly, and bundle what is left.
The test for whether something deserves its own listing
Would somebody search for this specific thing? If yes, list it alone. If they would only ever come across it while browsing, it belongs in a bundle.
That test is better than price, because a cheap item somebody actively wants sells faster than an expensive one nobody is looking for.
If you bundle
Say exactly what is in it, and photograph it all laid out together. The whole risk in a lot is the buyer expecting something you did not promise.
Say what is not included — no box, no papers, no spares.
Price the start low. A bundle with a high start price does not get going, and a bundle that does not get going sells for the start price or not at all. How to list a bundle
If you sell singly
Do not list all thirty at once. Run a few a week. Flooding your own store means your items compete with each other, and the ones at the back get no attention.
Start with the middle of the collection, not the best piece. Learn on something where a mistake is cheap. I inherited a collection — where do I start?
The case for one lot, honestly
Sometimes it is simply right: you need it gone, the space back, the matter closed. A single sale at a fair price today can be worth more to you than a better price spread over six months.
That is a legitimate choice and nobody should make you feel it is leaving money on the table. It is buying your time back.
More: how to list a bundle, I inherited a collection, how to price for auction.