I love Dragon Age (DAO and DA2, haven't play DAI yet) and just started with ME now for the first time. Both are great in storytelling and characterisation. In fact, I think Garrus might become one of my favorite alltime Bioware companions (which would put him in good companionship with Kivan, Jan, Zevran, Sten, Anders, Varric, Mission, Mira and some others).
The gameplay is different, but I found it easy to adjust from DA to ME. The areas in DAO are similar: You have five or six big areas (plus Ostagar and one different area in the human noble origin) with main and side quests, some random encounters on the road and some areas, that only open up, if you do certain quests. But mainly its a handful of big areas. Luckily there is nothing similar to the Mako. I do so suck in driving that damn thing, I always imagine Garrus sitting there wheeping because my Shepherd hits every rock there is
and he has to repair it later on the Normandy.
What I don't like in ME are those planet quests, which are kind of repetative and boring. They could have combined some of the very short planet quests to one or two bigger ones, That's a bit better in DA imo - there are fewer sidequests and they are much more interesting (Crime Wave is my favorite and those silly quests, you can do for the Mage Collective).
But of course, I can only compare to ME1, I haven't played the others yet