I think W3 looks way better than DAI.
More detailed and with a more realistic art which makes it look more beautiful. DAI still has a cartoonish look.
I mean, look at the clothing of the NPCs in the W3. It's amazing the level of detail. The facial animations compared to the BioWare still reusing animation all the time making females walk like gorillas. I remember I even saw in DAI one scene of my male inquisitor with the female inquisitor movement.
The change of weather, the wind blowing the trees, the details in monsters. The W3 is obviously more demanding.
DAI have loading times to close the game and to go to the main menu.
TW3 isn't more demanding. Or at least, both games do nothing to put my PC through their paces; it may be that on a worse machine TW3 would be demanding. The faces, like I said, aren't a good contrast because TW3 (and TW1-2 as well) used custom models. The NPCs are higher res but they're clones ala KoTOR, so it's a give and take type situation. On the one hand, stronger models. On the other hand, punch in the nads for versimiltude. Not that DA:I doesn't use recycled NPC props, but they at least tend to keep them to the background most of the time.
The environments are very different, better done in TW3 because they're portraying wildnerness better, though I think DA:I had a lot of visually impressive sights as well. I suppose I find TW3 underwhelming because it just looks like the various parts of Canada I've hiked, even though I can recognize the achievement in creating it virtually.
The loading times, though, again, are a problem with your hardware. On an SSD the only thing taking more than 2-4 seconds is the product of TW3's mandatory VO (which you can of course remove via mod).