I'm not going to say anything negative about the SDB, I know that most owners love them. I'm just not a fan.
My 30 year old 550 is the most versatile and reliable progressive out there. I love it, and I can crank some numbers out quick if needed even though it is a manual index.
I would think in your case that YOU would prefer the auto indexing 650 since that is what you are used to.
I will add this, I sure wish I had not have waited 20 years to get my first 1050! The ultimate, and worth nutting up even if you can't really afford it.
Best