...what are the benefits of a stainless steel bike? No problem with rust if permanently stored outside and used on salty roads during winter?
I wouldn't count on that, John. Stainless steel comes in many varieties and most of them are "rust-resistant" rather than "rust-proof", and the others are not rust-proof either but corrode slowly enough to excuse careless speaking. However, the ones that don't corrode over bicyclist lifespans are horrid to work with in approximately direct proportion to their invulnerability to the elements and salt.
Decades ago I designed the chassis for a large nostalgicar to be driven by a V12 engine. Since the thing was to be pricey and production capped at 100 by Euro type-approval regs, we contemplated getting it built in stainless but the welding was such a pain, in the end we put a few stainless subframes on the prototype which was otherwise built of steel -- until the fitters rebelled, saying the laser cut holes in the stainless were impossible to ream or bodge. I brought out my own notorious boss bodger and in dead silence opened up the bayonet (I mean literally; the thing was a WW1 soldier's knife with a bayonet about six or seven inches long); even the strongest of the mechanics succeeded only in bending the tip of the bayonet! We built the production chasses in steel and sprayed them with zinc instead. Quite a few years later I was in the proto shop supervising the shortening of a Bentley chassis for my summertime picnic car, when I spotted an interesting very large chassis outside against the fence: it was my unzinced steel proto, which wasn't in much worse condition than the stainless subframes which remained n it, as measured by scraping off the superficial corrosion and putting a rise-and-fall gauge on the depression left. On the way back to Cambridge I stopped by the builder of the nostalgicars to tell him to save the money he spent on zinc spraying (for which the prep is a labour-consuming and hence expensive business). He'd studied the proto through the fence when he drove by the year before and had since formed an opinion that the stainless was a dead end even for specialist engineering of our kind.
Having had painful experience of small-tube welded titanium space frames (they break), I'm not a fan of ti either, and would actually prefer stainless to ti if they were the only choice.
Personally, I think foamed aluminium, bonded together down the entire longitudinal centreline of the bike, is the future of bicycles, with steel as the longterm survivor for the niche markets. You'll notice I don't even mention carbon fibre; it's a short term distraction; in forty or fifty years people will be nostalgic about the "lost bicycles" of the carbon era.
I have a couple of perfectly good ali bikes but can't think of circumstances under which I would choose an ali bike over well-proportioned steel; steel just has greater kinaesthetic satisfactions and fewer of the micro-irritations that lead to repetitive stress injuries.
