Dad and I just bought Triumphs within a week of each other. I went with the Rocket Roadster and he went with the Thunderbird.
They are completely different bikes and the TB is a GREAT riding bike. However, coming off the rocket to his TB, I feel like I'm on a kids bike with pedals. It's 1600cc and has plenty of power but it's really smooth and rolls on the power easy. You still get up to highway speeds quickly but it's really no comparison. The sitting positions and the feel of the bike going down the road is different.
If you are going new bikes - I think you would be fine either way as far as reliability. Every manufacture will have those "stories" of bad bikes making the market but buy the extended warranty and give yourself some additional peace of mind.
WOW - now that would be a great setup - my son and I sort of have the same deal going on - only I bought a Speedmaster and he bought a Honda 750 Shadow -- his Honda is perfect for him and he prefers it over my Triumph - that would be ultra cool if we had the TB and R3's ! Yep, that extended warranty would be a no brainer for me with a new bike !