For the record: Rainier was climbed before in similar or less quality shells.
I see is 400$ for Trilogy and 100$ for Fitz Roy ... It's hard to compare this two jackets.
However, I would use Fitz Roy for my biking commute to work, not for Rainier.
Trilogy GTX is a new GTX Active Shell and it's amazing what they accomplished (390g for a fully featured mountaineering shell). To be successful on Rainier you have to pack light but not make mistake and leave something at home. Wind there is relentless and Trilogy will be great protection. Saving you made for not bringing heavier shell (300g) will pay of when you pack fully featured steel crampons 900g - 1000g.
I don't own Trilogy GTX but I have K Expert Evo GTX and its 680g. It's an excellent jacket and I love it. If I have some money I would buy Trilogy GTX and use it for all my Summer alpine (and for Rainier too).