The other thing to consider is the underlying usefulness of the week you buy. If you like Marriott resorts and want to stay EOY at whatever resort you buy and use II to supplement your travel with getaways, the Marriott purchase can make a lot of sense.
If you’d be equally happy with a non Marriott resort, then there’s no advantage to buying a Marriott unit EOY. Just buy whatever you like that trades in II. You’ll have access to getaways with that strategy.
If you’re not ever looking to use the unit you purchase- ie you’re expecting to trade your EOY unit in II and supplement with getaways- then but a good cheap trader.
I own two EOY Marriott units and one EOY Hyatt unit. There’s no downside to an EOY Marriott. Unlike Hyatt where you pay full club dues every year ($200ish) even though you only have usage EOY.