As someone who has put 70+ hours into HW and 100+ hours into FE:W, I have to go with FE:W.
Note: All of this is about post campaign content. The games are relatively even if you just plan to play the story campaign and bounce.
I won't refute most of what has been said in this thread about content. HW is brimming with it, but my main issue that keeps stopping me from going back to HW is grinding. It's just layers and layers of grinding. The actual overworld requires you to have specific items to unlock challenges (which require a guide or incredible knowledge of the original Zelda to even know what to do), so you have to go to another challenge (which will eventually often be a previously completed one) to get the item before you can even get the reward from it. Edit: this is apparently a relic of the past! it's been altered in the Switch version to allow you to purchase items instead of grinding for them. So that's nice.
Once you're in a fight in HW and you encounter an officer, you will have to wait for it to attack you, exposing a weakness gauge which you then try to deplete so that you can unleash an attack that really feels like the only way to fight an officer. The officer combat turns into a very slow game of waiting for an attack so that you can counter.
Bosses in HW are pretty impressive and neat the first time you fight them, but become a chore after the ~10 or so times you've already encountered one. The bosses usually have some sort of equipment that can trigger a weakness (ie. hookshot or bow or something) and they end up working somewhat like the officers. Wait for them to do an attack that reveals their weakness and hit them with the equipment that allows you to damage them.
Like someone said above, HW has highs (cool bosses, great characters with unique move sets) but, for me, it hit those lows so much when the grind sets in (described above).
I honestly can't bring myself to play more HW, every time I load up that adventure map looking to complete one more challenge, I just turn it off when what I described above sets in.
To FE:W, well, it doesn't have the above. It has more strategic gameplay allowing you to bring a certain number of units into a fight (usually 4) and freely switch between them while giving orders to the ones you aren't using. The games grind rests in the upgrade trees, where if you wanted to upgrade every character (which is a madman's goal anyway), you'd be looking at repeating a lot of content over and over. Otherwise it offers enough individual challenges in it's post game mode that doesn't make it seem like too much of a grind. Also the bosses in FE:W suck too.
TL:DR If you are looking to play only the story, they are both great games, but after the story HW has one of the worst and most grindy post game experiences I've had in a Warriors game. Fire Emblem was pretty fun throughout and I still occasionally go back to it.