Quant S&T Rotation vs FAANG Software Engineering

So I've received two full time offers: One for a rotational program at a Canadian investment bank (BMO, RBC) and another as a Software Engineer at a FAANG. I've done internships at both and enjoyed both places, but I'd really like to do more than just pure software engineering, and the prospect of using more math and stats in my work is exciting. I've also grown a liking for Finance, as there's tons of mathematical and engineering applications for it. However, the compensation at the FAANG is about 33% more. Moreover, from what I've read/heard on the street, it's no secret that sell side S&T is not quite a growing industry. 

What I'd like to ask is, does comp generally increase once you're out of the rotational and actually on a desk? How much can I expect in my second year? I'm assuming it probably still won't mach the FAANG offer, but if the spread isn't too wide, especially after taxes, then I won't mind taking a pay cut for a year. 

Also, is there still a real prospect of becoming a trader on the sell side? I know it's really competitive these days, but is there a realistic chance?

Thanks!