The short version
Two sub-$700 portable PEMF devices. Resona is the honest, protocol-rich, app-controlled budget winner. OlyLife is acceptable only if you discount the terahertz marketing.
When Resona Health VIBE is the right pick
If you're PEMF-curious and want the cheapest credible entry, or you want a portable wearable with 130+ documented protocols and app control — Resona is the right shape. Honest marketing, direct distribution, 2-year warranty.
When OlyLife TERA P90 Plus is the right pick
Only if you find a specific deal, explicitly discount the terahertz claims, and value the handheld wand form factor over Resona's wearable. The PEMF component is real; the rest of the marketing is the editorial concern.