You guys have covered this very well....my input as usual is not necessary.
But as usual I am compelled to move my lips and make incoherent noises
(I feel left out if I don't)
so, just some quick thoughts...
When I first started card modelling, I bought 110lb cardstock from Staples.
I fell in love with it and used it for every printed model of any scale.
I shyed away from very small models so the card weight was not a big issue.
When I started designing my own models, I started dealing with much smaller parts
and so I tried 65lb cardstock.
It was also cheaper and more readily available in the shops.
To be honest, it is now my main choice for all building, it is a good balance between thin enough to roll fairly tightly
and heavy enough to support its own weight (unlike plain paper).
I use 65lb card when calculating in the design process.
I allow for .22mm card thickness in all related measurements.
(I think 110lb card comes in about .27mm)
And just one more thought:
if you are like me, you look for deals when buying cardstock.
I often look for the cheapest prices
...but I have learned that cheap quite often relates to poor surface,
bad print quality and overall disappointment.
It is definitely worth paying the extra few dollars for the brand name or better product.