Boilers for Forced Hot Water System

P_G_

Hello! I'm hoping to get some feedback on boilers and water heaters for my house.
2-family brick house in Rhode Island, built in 1950. Two adults in each apartment, one bathroom each, +laundry. Separate gas meters for each apartment.

Forced hot water system with wall-inset cast iron convectors. The current boilers are 70-yr-old oil boilers and the water heaters are 9- and 10-yr-old gas heaters.

I used the Slant/Fin heat loss calculator for my apartment (1st floor) and got 38,410. I'm assuming 2nd floor apartment isn't too different.

Proposals from different contractors (for identical systems for each apartment)

1. Viessmann Vitodens 100
   
2. Williamson GWA-070 Natural Gas Fired 70k BTU 83.0% AFUE
   
3. Burnham ALP-080 95% AFUE modulating condensing stainless steel, Crown MS2 40 gallon indirect fired water heater
   
4. SlantFin VGH100CH wall hung condensing gas boilers, HeatFlow 40 indirect water heaters
   

Comfort and reliability are my main concerns, as I plan to be here long-term.
Opinions on traditional vs modcon with indeirect vs combi for this situation?
Opinions on the proposed models?

Thanks for any input!

STEVEusaPA

Why did you start another post? I'll see if @Erin Holohan Haskell can merge the two.
I thought we did this already. All your boilers are severely oversized.
If you need 38k, you don't need 100k.

HVACNUT

I thought I had Deja Vu.

Erin Holohan Haskell

Thanks, guys. @P_G_ asked to start a new post.

EBEBRATT-Ed

I vote for cast iron but there is no right or wrong choice.

Cast iron=lower installed cost, better parts availability. longevity?

Mod con=higher efficiency, higher installed cost, parts availability can be an issue. longevity?

P_G_

@STEVEusaPA sorry for confusion. The first was too long and information was getting lost. I wanted to start over and simplify.