VWP or valid B2 on expired passport?

[sn0skier 0]

USC living and working in Chile for years that recently got married to a Chilean citizen. We then filed our I-130. I need to move to the states in the next few months and my wife wants to come with me for the beginning of the marriage (we are having the chapel ceremony right before we leave) and then return while we wait for the I-130 process. Chile recently got on the VWP and my wife's passport expired around the same time. This passport had a B2 visa in it that is still valid. She got a new passport that works with the VWP, but, as the B2 stay time is longer, is there any reason it would be beneficial to apply on the VWP too? Would there be any drawback to applying for the VWP?

Side note: if the 1-130 process requires us to be back in Chile before the stay length limit, we would like to do that, hence, we don't want to buy the return ticket earlier than necessary. Does she have to have a return flight ticket with a set date when she enters the country on a B2 or VWP? Is it risky to not have one?

[Hypnos 6,576]

If she has a B-2 then it makes more sense to use that since it offers (slightly) more benefits for the alien over the VWP.

You are required to have a return ticket if you attempt entry on the VWP; you don't need a return ticket for a B-2, but it's highly recommended you have one because it will usually give CBP an avenue to deny entry (or at least ask a few more questions) on a B-2.

[sn0skier 0]

Is there a reason to not apply for the VWP as well though? Does applying to the VWP get rid of the B2?

[Hypnos 6,576]

There's really no benefit to applying for an ESTA for the VWP when she already has a B-2.