pre-1981 911s, low miles on odo, or higher miles with records value
 

Carfax report only goes back to 1981.
my question is, low odo miles(let's say 40k miles) pre-81 911 with no records can be easily made, and list on the market, cause there are no way to verified by Carfax or so..
however, an honest car with records might be a sub 200k miles car, but records from early 70s or 80s can verified how the car been through.

assume they are both in same condition and same year, only difference is mileage on the clock, and records.

which one should be worth more?
if it's same price, which one would you choose?

Eyeballs are key. A pre 81 with less than 40k is a rare bird and would raise multiple red flags for me. I'd be all over that thing like a hound dog, and get a tech involved as well.
The 200k deal with records depends on what the records say, when they say it, and what your gut tells you.
If was choosing first, I'd heavily inspect the low mileage example. A lot of upside if it proves to be true.

I would buy the pre-1981 911SC that has the title washed, the meter turned back and modified, Hurricane Sandy salvage vehicle that has been hosed out with the dead fish still floating in the smuggler's box.

Seriously, to find such an early SC, low mileage gem other than buying it from some one-owner Doctors estate, there is no way of telling. I would say 9-out-10 911SCs that are advertised with this mileage are fakes - much like most of Bob Dylans autographs.

And to add to CountD's comments, 2/3 of them will be nicer than the 200k car. If the car looks close to nice enough to be an actual 40k car, get a PPI, and if the results concur with surface appearances buy it.
A 200k will be harder to resell. This matters unless you are looking for a forever car.

My '67 912 showed up with the odo zero'd and no records. Do I care? Nope. Condition checked out in accordance with what I was paying for it so I bought it.