For the first example here I agree with you that options with 4-5+ is better in a dropdown, but in this case the radio buttons are better UX from my point of view.

Options are shown in a simple and clear overview , 1 tap select, visually appealing. By the looks of it you could fit up to 8 options.

The dropdown would require 2 taps and if shown on a mobile - a native list picker would cover the nice headphones image, or if custom made either be longer than the screen or a scroll needs to be inside the dropdown.

I would also order the models alphabetically and start with HD 200 unless the XD models are the latest and most sold ones maybe.