To Rewton:Eight hours of sun ,in your zone (7),is not enough for this large fruited cultivar.
It would be enough if you was growing it in Fresno Ca,but not in zone 7.
In your zone and mine 8 hours of sun for Kathleen black is only marginal,so it is just normal to have problem making it fruit abundantly.

I have found even when I put figs in full sun in my zone it helps on good years significant;y but one years like this when it is cold, the figs come much later than normal and suffer.  In a year with very warm weather it still does not hurt them to be in full sun, it actually helps to have the extra heat in ground or in pot, only difference is I have to water more on those warmer years.  Some varieties can be put in 3/4-2/3 sun and get decent results, but what I have seen to those trees in the shadier spots seem to also do worse in winter, I think this is because they don't have as much reserves as the trees in full sun.  Would you say that you have seen similar things happening Herman?

Chivas: One Hundred percent I agree with you.
Also the larger the fruit the more is  dependent on full sun.
In cold climates,Zone 6 and 7,fruits will not form early in Spring,if it is a cold Spring,but can be forced to form early by insistent pinching,and placing pot in full sun,or have the plant ,planted in full sun.
Only if one manage to make the tree form early fruits ,they will ripe in cold zones,as mentioned.
Of course a greenhouse will help in Spring to force plant form fruits inside then take out plant in May and keep growing.

Best way to find out is to grow them side by side and compare them when they have reached maturity. 
Nothing to lose in this case since they both look like very nice figs. 
I volunteer do you want my address to send me cuttings..LOL

Vasile, regarding zone 7a being marginal for Kathleen's Black and De La Reina (planted in ground) you may be correct.  However, I thought that one of the main advantages to Kathleen's Black (along with the large, tasty figs) was that it is not a particularly late fig.  Is this not the case?  I've never seen the KB planted in ground at Gene's old place in Washington DC (only a few miles from me) when it is fruiting but I have heard reports such as persianmd2orchard's above that it has decent productivity.  That tree is planted in his front yard, close to his porch, and the front of his 2-story house faces the west.  So I doubt if it gets any more sun than mine does and quite possibly less.  So I am still holding out hope for next year with my KB and am hoping De La Reina can be grown successfully here as well, although I think I will grow the latter in a container at least initially.

Steve:Check out Chivas post and you will see he is correct.
In good years,(with warmer ,longer Summer),large fruitted figs get ripe just fine,but in the last 5 years every year was difficult.
Cool rainy climates,Cold Springs,Cold frosty Autumn nights,every year it was ,a difficult one,so in such climatic conditions only full sun will be enough to get a good harvest.

Hi all,
The tomato growing test is a good one. If tomato do not fruit properly with proper watering and fertilizing, than fig trees will have a hard time to fruit properly.
I'm in Zone 7 and had an opportunity to plant trees at a second location . Both locations are 25/30 kilometers from one to another - so really nothing in terms of distance - both are at the same height above sea level.
At the second location growing tomatoes is hard - at Springtime frosts last 10 days more and they come 10 days sooner at Fall time, and
overall the temps are more harsh than in my own garden.
3 strains were at that location and the only one fruiting some years was the ufti "unknown from the Italian gardener".
I now have the two other strains in my garden. One strain already fruited for me this year and I'm expecting fruits from the second come next spring.
So local conditions even in the same Zone make huge difference. I'm not even mentioning differences between trees in shady and sunny spots , and between well cared trees or left alone trees - that is proper watering and fertilizing.

This thread has strayed a bit from its original purpose (sorry Axier!) but I think the discussion is very valuable.

Chivas, let me make sure I understand your points.  Correct me if I'm wrong but here is what I extracted from your post:

- Full sun is always advantage for figs compared to partial sun but isn't the whole story because you also need heat.  In northern climates this is often limiting.  (Microenvironments that retain heat would be helpful.)

- Figs that grow in part sun can do well in years with a lot of heat and a lengthy season; however, they might not be able to withstand cold winter weather as well because they store less energy reserves.

Steve, that is exactly what I have observed.  This has been for my zone, close to yours but a bit colder in winter and my guess is a bit cooler in the growing season overall.  Even in pots I don't see a disadvantage to put them in full sun, the more the better at least in my experience.