The flippant answer: The film you have tested and calibrated for those conditions. This assumes you have worked out a personal EI and development scheme for the contrasty situation you describe. Any film can give good results if you expose and develop appropriately.
The less flippant (long) answer: Note that in the following I am assuming that you use the in-camera meter or another "averaging" metering technique (if you use a spot meter to measure the shadows, the following will not apply).
Contrasty lighting and "standard" metering using an in-camera meter usually gives negatives that are underexposed and contrasty (assuming a "standard" development time). The real danger with contrasty, bright scenes is that an in-camera meter will usually not indicate enough exposure to keep detail in the shadows, thereby giving you featureless shadows. To prevent this, you need to make sure you give adequate exposure to record the shadows. Contrary to intuition, you will need to expose more in contrasty bright situations than in "normal" situations. With bright scenes with harsh shadows, I would imagine that a stop more exposure than the meter indicates would do the job for 90% of the time. When the clouds roll in, or the sunlight is softer, go back to the indicated reading.
Again, expose more than the meter reading for contrasty scenes.
Secondly, for contrasty scenes you would ideally develop less. However, as noted above, giving different development to different frames on a roll is impractical. If you do have a roll entirely exposed in the bright, contrasty situation, and you are getting good contrast with prints of scenes with "normal" contrast, you could develop that roll less. The best way is to test, but if you develop 20% less and have given more exposure as described above, you'll likely end up with very printable negatives.
If there are many scenes of different contrast on the roll, you could reduce developing time by 10% and then compensate with paper grade.
Again, I believe that giving adequate exposure is more important than film choice in contrasty situations. The real problem most people who use in-camera meters have is that the meter reading for scenes with a larger-than-normal contrast range is wrong. Just overexposing those contrasty scenes by a stop and adjusting with paper grade will give much better results.
When I shoot roll film (which is rare anymore) I always "underdevelop" a bit; i.e., my rollfilm negatives are developed so that a "normal" contrast scene prints well on grade 3 paper instead of the grade 2 I shoot for with sheet film. That way I have grade 2 and below to deal with contrastier negs.
If you are developing so that a normal scene prints well on grade 2, you may want to reduce development time for rolls that have any scenes of extreme contrast to make those easier to deal with. Again, I would test so that a normal scene printed well on grade 3, but reducing development by 10% as mentioned above, will take the edge off the most contrasty negs and still allow printing of the others.
There is a lot of refining you can do with this system, but the basic principles are: make sure there is always enough exposure for the shadows (which means more exposure for contrasty situations and normal exposure for the others with in-camera meters) and make sure that you don't overdevelop (which means finding a compromise developing time that underdevelops some scenes a bit but doesn't overdevelop the contrasty ones). Contrast adjustment is then done at printing using paper grades.
Sure, there are film and developer choices to be made here as well, but they will not have nearly the positive effect that simply exposing correctly (i.e., giving more exposure for contrasty situations if you use an in-camera meter) will have.
Sorry this got a bit long, but I hope it helps,
Best,
Doremus Scudder
www.DoremusScudder.com
