Can only talk about reliability of the first gen, on my FR-S I had 9 years of worry free motoring. Genuinely nothing went wrong on that car mechanically or electrically. The only car I’ve ever had that I spent $0 on any malfunction. Not even a recall, which seems rare these days.
I’m only half a year in the 2nd generation, got BRZ this time. Also zero issues to report but it’s also new too.
You want 1st gen to 2nd gen or GR86 vs new BRZ?
As a Canadian the biggest advantage in both generations was price. For some weird reason Toyota wants to command a price premium for these cars. Something like $2K-3K extra for the same car. It was different when Scion still existed though, Scion was always cheaper but just a bit cheaper.