Oil 2 Gas conversion

Hello,

In getting quotes for oil to gas converstion started, I received a quote from some folks in my area near hicksville, ny.
currently have a oil fired boiler, indirect water heater, 275 gallon in basement (above ground) oil tank.
These need to be removed and proper permits filed with nassau county of course.
Have only a single bath (with potential for 1 more bath in the coming year, which will determine hot water output). have a dishwasher and washer dryer combo as well.
i did inquire into a few boilers and I'm leaning very much towards a Bosch Greenstar 151 Combi.
I am getting decent quotes but nothing substantial enough for me to say "you're hired".
I did want to raise a concern.
One of the guys who came by wanted to sell me a Bosch Greenstar 151P instead of the full fledged 151.

What am i missing apart from included expansion tank within the 151 that the 151P doesnt have.
I am getting quotes for a doing the necessary controls for a 2nd zone for the basement heating (not the heating, just the controls to expand it at a later time).

thanks
cchhat01