The other thing to consider is if you'll want to keep working at the company after so many people have left due to the buyout and the layoff. If not, taking the buyout and looking for a new job is likely to be better for you than not taking the buyout, not getting laid off, and looking for a new job once you conclude you don't like the new environment. For one thing, you'll probably have buyout compensation and new job compensation at the same time; for another, it may be easier to find a new job if you're in the market before the layoffs increase the hiring pool.
tl:dr One round of layoffs isn't bad if you're staying, but subsequent rounds can make you miserable.
also means they can dodge any NDA / wrongful termination / bad behavior issues on the way out. sign the doc and play nice and get $$$.
keep in mind the US doesn't have great protections in that regard, so "severance" may be them allowing you to collect the last of your crap on the way out and paying you through the end of the week.
I know its very similar to the equivalent amount of cash but it feels a lot different. I feel like half my desire to work is connected to healthcare for the family.