I would say 6' but that is my opinion.
Your pool is not really long enough for 8' deep.
Example: 8' starts 8' from the end. Max slope from deep to shallow is 3' of run for every 1' of rise. So to get to 5' deep takes another 9'. So that leaves you with 15' to go from 5' to entry depth, 3'6, or 4'. This is the only area you will be able to stand in. Deeper pool stays cooler(maybe plus or minus there), and if heating makes a lot more water to heat.
Resale could go either way, I know people that have not bought homes because the pool was deep, and others that wish it was deeper.
It really depends on your wants.

I wouldn't go deeper than 6'. No kids here either but ours is play pool depth meaning deeper in the middle max about 5'. Went with that for resale since this is a kid friendly neighborhood. I'm 5'7" husband over 6' and 5' deep is still good. We're usually lounging, floating, swimming rather than standing or diving in so don't need it any deeper.
Also more depth means more water, chemicals and more $ overall. May want to check with your insurance to see if depth affects rates.

We have the same size pool with an 8' deep end. We opted for the 8 feet as we have a child and she has friends, so we wanted to be on the safe side. Also, My husband and I dive in pretty frequently (we're 6'1 and 5'11 respectively) and 6 feet would just feel wrong. You may also want to consider re-sale value. Do you live in a neighborhood with lots of young families? Will a new family expect a more versatile pool? Hope that's helpful.

I went six and wish I had gone deeper. Yo do not fill the pool up to the top so my overall water level is about 5' 10". I am over 6 foot tall and wish there was a place where it was deeper than I am tall. Plus on a hot day the deep part is nice and cool.

We went a little outside the box and did 4' - 7' as our pool is only 31' we figured this would give us enough shallow and deep with a nice transition. Still in the building process so can't testify yet if this is the best idea.

We are in the middle of our build. We had originally opted for 4' shallow and 7' deep, as I wanted adults to be able to swim laps with no problem. We then opted to make shallow end 3.5', as that is more the norm out here. 3.5' means more conventional (for resale), and also more kid friendly. 7' means nice cool deep end, with plenty of depth for diving. Our pool is going to be 32' long.

Seven foot is not adequate for diving. You will potentially smack your head on the bottom. Eight feet is the minimum for a diving permitted pool by construction code standards.

Scott

I think that deeper for diving is better. Scott certainly knows the code standards, and my two cents is that the height of the person diving also affects the needed depth. Our pool is 8' or 8.5' deep, and plenty for me (5'4") to dive off the board but my 6' husband is not comfortable diving in it. He skims the bottom with his hands every time so has to be very careful with his diving. Our T shaped pool has a pretty steep slope from the deep to shallow end, too.