Just wnt a bunch of opinions....I know how they both work..more or less...A magician mentioned to me that no one sees dollar coins anymore and it may raise suspicion...so he rcommended staying away from the $2.85 trick and he recommended that I buy the $1.35 because half dollar coins are more ordinary (wrong word)

No one sees half dollars either so I don't think it makes much of a difference.
The dollars in the $2.85 set will obviously be larger so easier seen for larger groups of spectators.

The 21cent trick is good to seeing they are everyday coins .

Another point to consider with these sorts of sets: locking, or non-locking?

Discussions are quickly becoming moot about what coins are best based on whether they are typically carried by folks. People carry loose change less and less. I never carry loose change, and I have a small amount in my car for parking meters (and parking meters mostly all take credit cards these days).

Coins are becoming props like cups and balls.

I think it’s best to select whatever coins fit one’s hands and are easiest for an audience to see for the performance.

At this point, given how rare dollar coins are these days, that only make it easier easy to work into the routine.
Something like "Did you know we used to have giant dollar coins? But they had a problem where they'd start disappearing - and cause other coins in your pocket to go, too, so they stopped making them". And then demonstrate the routine.

Or some equivalent, much in the same way that folks sometimes introduce foreign coins as having some odd property that local coins do not.
Mine is certainly not the best patter here, but rather a jumping off point to show that it's possible and encourage your own creativity.

As others have said, it's ultimately about what size coin you like the best, and would prefer to use.

I 100% agree with GJo. I myself am cash-poor on a daily basis, using my ATM card for virtually everything. I also keep whatever small change I might accumulate in the car for parking meters, but am now finding that even putting coins into such a device is also becoming a lost art. (The pile just sits there, uselessly accumulating.)

Never mind dollars or half dollars; if someone wanted to do a trick for me and asked to borrow a quarter, dime, nickel or penny, they’d be outta luck.

Maybe I should start thinking about tricks with ATM cards instead?

Naaaahhhh. I’ll just carry on, supplying my own coins. (We don’t often break into an impromptu routine by asking to borrow a deck of cards, now do we?)

(Unless we’re playing at a card table, maybe, but that too seems rare these days.)

I am thinking that perhaps you just want to purchase the version you like the best and enjoy performing it. Familiarity with the coins is not necessary. In fact, the uniqueness of the coin could add enjoyment for the spectator.

In essence, do not overthink it. Just enjoy performing which ever one you decide on.