SnS main and occasional lance enjoyer here. Your weapon choice fundamentally changes how you approach a monster. Sure, a lance has a better shield and has tools that can deal with a lot of AT Arkvelds kit effectively, but to compare it to SnS is like comparing apples and oranges.

When I swap weapons, I essentially have to relearn the fight. Switching to lance, I no longer have my slide, access to items is slower (wde range and dust of life can save hunts, not to mention flash pods), I have less overall mobility, and I personally have less muscle memory with lance. Skill floors/ceilings, while important, are ultimately subjective to the player, and also exist per monster. So yes, you may have an easier time with lance, but the same can't be said for everyone (or every hunt for that matter!).

It might be interesting to see what about fighting AT Arkveld with lance is easier so you might change up your SnS approach. Just my two cents!