I love it how TW3 gets praised for everything that it does better, yet when DA:I is discussed, it still gets bashed here, in a comparison (!) thread, for things that TW3 completely failed to implement or did it at a minimum bare-bones level. Like the scope of variety in role-playing your character. This is really objective comparison and feedback, indeed, no overreaction and one-sidedness. 
I personally see these few points that TW3 has over DA:I:
- side quests are more involving
- main quest in DA:I feels shorter in comparison
- more background NPCs, whereas in DA:I we mostly traverse desolate areas without many NPCs and hear them chatter at fewer places, like Skyhold and Val Royeux
- better graphics
- more detailed sfx (weather, day\night cycle)
And these few points that DA:I has over TW3:
- varied role-playing, as we can create a character with choice of race, gender, class + more varied dialogue responses and reactions
- companion banter of very good quality in addition to NPC chatter
- more varied combat + more varied ways to play it (pure action with or without pause, tac-cam)
- chooses to appeal to wider audience (which, in turn, creates more role-playing opportunities)
- a party (while you can still choose to play solo, a party allows for more tactics and variety)
I could name other points, but those would be highly debatable. Like which game does side characters or romance better, etc.
TW3 over DAI:
I don't know about the graphics. I can see someone thinking that the scenery in DAI is more interesting, because it is more artistic and tW3 goes for more realism. Animations, facial expressions and textures are not on the same level, though. TW3 wins hands down. The art direction in both games I think is solid, though.
DAI ovr TW3:
1. Varied roleplaying: In DAI your guy (or girl) looks different, but the overall story arc do not strays too far, regardless of your appearance. I do not see that difference in roleplaying The Witcher and roleplaying The Inquisitor. DA players tend to use a lot of head-canon due to the involvement with the series. It does has more variation visually, but in terms of reaction to what my character does and speaks I will have to give the nod to TW3. Without spoiling much, you can start a brawl or happily drink with some thugs, at several times you can chose between live and death of several NPCs, you can be cruel or a nice guy. You are always Geralt, but there is more range to work with TW3. Yes, you can play an Elf in DAI, but the life story of your Elf Inquisitor will not be that different from my dwarf inquisitor while my daughter's Witcher is a nice guy, that has discounts with most vendors and my Witcher was responsible for the extinction of at least two settlements and is a complete ******.
In DAI you can play several guys with some variation between them, in TW 3 you can play one guy with more range between being good or bad and more outcomes based on your decisions. For example, in DAI you can chose between mages or templars as main allies and in TW 3 there is a particular quest that has more options on who will appear to help you, depending on what you did during the game.
2. I talked a lot about combat in other posts already, but I will summarize here: I think combat in DAI is a dumb MMO light affair. The tactical system is broken and the great advantage of having a party is wasted in the system - it is way easier and quicker to just control one guy. The animations do not have weight to them and it is so automatic that my son with one year and eleven months can press buttons randomly and destroy 80 to 90 percent of the enemies (he cannot fight dragons and bears, obviously and I have to adjust the camera and move the character a bit sometimes).
TW 3 is quirky, with uneven enemy forces spread around and is overdependent of the dodge button. That said, if you play thinking like the character, or roleplaying the Witcher you are supposed to be (studying your enemies, using signs, using bombs, timing your strong and quick attacks) it can be very rewarding, more than it has any right to be due to its shortcomings.
I got the feeling that I learned to be a badass in TW3. In DAI I learned to avoid the tactical cam like the plague.
I guess, in the end, in both games you have to overcome something in order to get the best experience possible, but I got the feeling that I had to use some skill and roleplaying in the Witcher and in DAI I had to use lots of patience. It is way more easier to avoid being trapped in the scenery than teaching Varik to keep his distance.