One huge asset Valheim has over 7 days to die is that, as some have stated, time is no issue. You could be grinding the starter biome for 20 hours if that's fun to you, just casually hunting birds and deers, or you could try to rush as quickly as possible to the next biome until you finish the game (or get rekt and realise you need to prepare). This also brings a level of flexibility 7 days doesn't have. We've had days with my group where we really wanted to push it and get a challenge, and then there were days of "let's just hunt some meat and feathers and maybe do a low level cave because we need early game mats". You can't do that with 7 days. The way the game is designed, it's basically a rush against the clock to be prepared by the next horde. Sure, you can turn off hordes or just play on 2 hours days with easy settings, but then the whole challenge is gone for the entirety of the game. You can't just hop in and do whatever you feel like depending on the day and your IRL energy level, you'll have to live with the decision you made when you first started playing (unless you constantly change settings which would feel gamey to the point of being close to cheating the game).
In addition, the biomes really feel different, as in, different monsters, different ressources, different milestones in crafting/building. The biomes in 7 days feel like basic reskins with the odd wildlife difference, but zombies are all the same especially in their mechanics. Hopefully A20 will turn that a bit around, but unless we get special creatures for the harder biomes, just "raising the gamestage" won't give biomes a different combat feel. Oh yeah, combat. Valheim's combat is simple but it's fun and engaging. 7 days melee combat is quite frankly subpar on so many levels, especially compared to how awesome the game is in other areas.
Lastly, bosses. We've had crazy fun doing the 2nd boss to the point we're thinking about picking up Monster Hunter. There's a great sense of adventure when you sail off with the purpose of defeating a boss in Valheim, and a great feel of accomplishment once you're done. There's really no milestone in 7 days that is comparable. Sure, the hordes are fun, but the aftermath doesn't change jack to your game besides you having repairing to do and less bullets to expend.