Many local HVAC companies just guess the size of the AC unit and therefore I
decided to run my new house data through a Manual J compliant software.
Depending on design summer temperature I obtain the following AC size (in
tons) recommendations

Summer Temp Size 1 Size 2
90F 4.76 6.02
95F 5.04 6.46
100F 5.32 6.89
105F 5.61 7.33

The house is being build near Seattle where the max summer temp rarely
exceeds 105F but gets to 100F for a week or so during summer. 90F can stay
with us for few weeks per summer.

I am a bit confused about two sizing recommendations:

Size 1 is based on sensible and latent heat gain
Size 2 is based on 75% Sensible Capacity

I do not want to oversize my A/C unit but I do not want to significantly
undersize it either. What do you think? Thanks.