Hello Benjamin,

I am a fan of Astia 100F, too. One of my favorite color films. I still have enough of it in the fridge for the next three years.
Nevertheless I have used Provia 100F a lot, too. Like Astia 100F and Provia 400X, one the best color films ever made, outstanding material. When this film was introduced 1999, it has set the benchmark for professional color films.

In addition to all the shots with these films in daily shooting, we've also tested all of them in our test lab. Short summary:
The main differences between Astia 100F and Provia 100F:

1. Color:
Provia 100F is strictly neutral balanced, with a very accurate and natural color reproduction. If you shoot it under norm light with 5600 K color temperature, and then compare the result of the Kodak color test chart with the original, you see that the film result is an excellent match to the original.
In comparison Astia 100F is bit more warmer balanced, with a bit more saturation in yellow and red.
That is the main, most obvious difference.
Rendition of skin tones is excellent with Astia, and still very good with Provia 100F. We've found skin tones of Provia 400X very similar to Astia 100F, therefore using 400X very often and successfully for Portrait and fashion shots.

If you use a Skylight 1A filter with Provia 100F, you get very close to the bit warmer balance of Astia.

In all the years I've never had problems with a general bluish cast with Provia 100F.
Well, if you shoot it e.g. in midday sun, when color temperature is extremely high, then of course you will see more blue. But that is just because the light is blue. The film renders it in a natural way. Nothing wrong with that.

But in this digital age, when photographic knowledge is in free fall , and lot's of people don't know anything about the huge changes in color temperature of natural light during the day, lots of photographers accuse the film for a certain color shift.
But in 99% of the cases it is not the film, but the color temperature of the natural light......

Another factor concerning color rendition which is mostly overlooked:
The color transmission of the lens!
Lenses do significantly vary in their color transmission:
Some have a very exact and neutral transmission, some have a slight warm or cool (blue) cast, some have a slight magenta cast. And some have some very heavy color casts.
We've tested various lenses from different manufacturers under norm conditions (5600K color temperature, Kodak color test chart), and the differences between the lenses (even from the same manufacturer) are clearly visible.

Interesting result:
The differences between color rendition of different lenses can be bigger than the difference between Provia 100F and Astia 100F!
E.G. my older Sigma 28-70 zoom has very heavy yellow (and a bit less green) color cast, making Provia 100F looking like a different film, very warm balanced. In comparison Astia 100F shot with my Nikon 1,8/85 looks like cool balanced film.

2. Contrast:
Astia 100F has a bit less contrast compared to Provia 100F: But the difference is subtle, about half a stop. In the dynamic range test we've got 8 stops with Provia 100F, Provia 400X, Elitechrome 100, E100G, and 8,5 stops with Astia 100F and Sensia 100 (in this test we've tested the range, where still a bit detail is seen in both the shadows and the highlights).
Provia 100F has a bit higher MTF in the spatial frequency range of 5-20: If you project Provia 100F and Astia 100F in direct comparison, you will see that Provia 100F looks a little bit sharper.

3. Grain, resolution:
Due to the data sheet Astia 100F should be even a bit finer grained than the already extremely fine grained Provia 100F. But in practical photography there is no visible difference: At 40x enlargement (projection on a screen with 1m x 1,5m) no difference can be seen.
At 100x enlargement (under microscope and on very big projection screens) a tiny advantage for Astia is visible.

Resolution at higher spatial frequencies is identical:
In our standardized resolution test (object contrast of 1:4 = two stops; test lens Zeiss ZF 2/50, f5,6) we've got the following results:
Astia 100F: 120 - 135 Lp/mm
Sensia 100: 120 - 135 Lp/mm
Provia 100F: 120 - 135 Lp/mm
AgfaPhoto CT Precisa 100 (current Fuji made version): 120 - 135 Lp/mm
Elitechrome 100: 120 - 135 Lp/mm
E100G: 120 - 135 Lp/mm
Kodak E100VS: 115 - 125 Lp/mm
Velvia 50: 110 - 125 Lp/mm
Velvia 100: 125 - 140 Lp/mm
Velvia 100F: 125 - 140 Lp/mm
Provia 400X: 105 - 115 Lp/mm
Elitechrome 200: 100 - 115 Lp/mm
Kodachrome 64: 90 - 105 Lp/mm
Rollei CR 200 (Agfa-Gevaert Aviphot Chrome 200): 65 - 80 Lp/mm
[for comparison:
Kodak Ektar 100: 90 - 105 Lp/mm
Fuji Superia Reala 100: 105 - 115 Lp/mm]

Here you find further test results from other test teams (with different object contrasts; including results from Zeiss):

These results are system resolution values of the tested films with the used lens in 35mm.
We've also tested it in medium format:
Lens: Mamiya Sekor C 2,8/80N, f5,6 (object contrast 1:4) with Mamiya 645 Pro TL:
Both Provia 100F and Astia 100F: 115 - 125 Lp/mm

If I remember right you're living in Northern Germany?
Maybe we can meet and I can show you all the examples in real life.

Best regards,