Platinum = cynical attempt to sell using the Focusrite name.
You have to understand the history of the company.
The original ISA Blue series were designed by Rupert, who listens to what stuff sounds like. 5534s are excellent op amps. I know you'll read otherwise, but consider the source: many of these people saying so are sheep rather than engineers.
Focusrite went broke after Rupert was beseiged and plagued by people begging him to make consoles. Despite £1,500,000 (about $3,000,000 at the time) in orders, the company cash flow was so inadequately set up for large-frame manufature that it crashed. Phil Dudderidge (of Soundcraft) saw an opportunity and bought in, keeping the name alive. Rupert was gone, but the existing designs were now Focusrite's property (and therefore Phil could use them)
The Red series was an attempt to make basically the same stuff, but with some cost savings. Many boards inside red equipment that I've worked on have had alternative parts placings for blue and red, so the same motehr board can be used, but perhaps with some transformers skipped here and there, or some cheaper pots or something.
The Green series was the cynical attempt to sell based on the good name of Focusrite, founded by Rupert's early work. It's totally transformerless from everything I've ever seen, the cases are cheap castings, the knobs are cheap mouldings. The gear sounds like utter crap and doesn't deserve to bear the same name.
The Platinum is actually branded as the "entry-level" Focusrite gear. I saw one once. It made me shiver just to be in the same room as it. I never looked inside it, but I felt utter certainty that if it really was a step down from the greens, I wanted no part of it.
My platinum experience is therefore insufficient to give an opinion, but the Focusrite history lesson should put the product lines into better perspective.
Rich, I get the distinct impression from your postings that you're influenced more by what you think something should sound like rather than actually listening to it... I don't mean this as a criticism, but it sounds like your friend summed the original design up nicely: a transformer, a 5534 and a high gain stage (the transformer was omitted from his summary)
If it's simple, it might just sould like gold. That's how it frequently was for tubes, after all!
Keith