Rust converters and encapsulators are very common these days and I don't believe any one product dominates the industry. All require at lest a wire brush to get to a solid surface to truly last.
So here is my personal preferences from experience:
1. Eastwood Rust converter followed by Epoxy primer then topcoat if its visible and I have time to do it (the converter has to sit for 48 hours to work).
2. If its not visible, then I use Rustoleum Rust Converter (spray can). Its cheap and works pretty well if topcoated. Generally for brackets and such where pretty is not a key requirement.
3. If its inside something (rail etc.) Eastwood Internal Frame coating (it used to be called something else) but it is very thin and seeps through and is heavy zinc content. Not for looks at all, leaves an ugly mess if it seeps out so careful.
I have tried POR-15, Silver Bullet, and the above as comparisons and that is what my preference is based upon. Others may disagree and I respect that.
RGAZ