Humans with varient human trait could be argued better than most other races because the extra feat is very very valuable with all feats available I would consider it over other races with the extra feat if you had access to every feat. Secondly fire resistance has a high value stat block. Since fire is again the most common source of damage and does remove the need for consumables in the same way. I mean if you look at consumables in the same aspect light spells compensate for dark vision which they do all have base dark vision and they do gain an additional ability at 5th level for all the tiefling races which is not present in game currently because the level cap is 4...

So your weighting +1 additional stat with a half elf mind you you do have choice currently vs tieflings which do not get full choice currently as all the subraces are not unlocked.
So +1 stat
+save vs charm, immune to sleep (which is less effective later on)
1.5 m movement or a cantrip of your choice

vs

fire resistance - Most common damage type in general.
1 additional spell like ability and another spell like ability you dont have access to at 5th level

Seperate downside note you dont get to chose your 1 ability boost very highly as a tiefling because you lose out on full racial options currently for tieflings as not all subraces are available.

Its not as lacking in balance as you might think if i didnt not like tieflings I could see a reason to consider playing one fairly easily especially with 5th level abilities however i do like the +1.5 m movement a lot because I do prefer playing melee classes and movement matters in that case. In same aspect there are alot of fights in balders gate where everthing around you gets lit up like a xmas tree with fire because well larion likes to use alot of explosive fire items on characters though its tone down from patch 2 pretty deciently its still pretty common.

If your cross compairing them vs shield dwarves currently shield dwarf is going to win because 1 stats are not rolled which they do get that extra +1 overall stat and armor which is pretty big vs losing 1.5 m speed. Depending what you want to do however 16 str and 16 con vs 17 and 17 there is no difference unless if your not taking the feat for +1 to 2 ability scores. If you are well then the dwarf has an edge for that which is where rolling stats would have a larger factor as the game goes futhers because that stat buff could be off set with a half feat well placed.

In the same perspective you do get the +2 cha which as a cha based class the dwarf does not. There are alot of things to weight in there as well as the fact not all sub-races for the classes are present and that does give more options in how you build your setup.

If you really like tieflings well that would weight in and you picking them for there utility and you would be looking more at what subrace is missing that would fill that gap. Additionally humans are op if they add varient human if they do not well yeah humans are not so hot overall for most classes as +2 +1 +1 over weights +1 to all stats. varient humans case your taking it because you want the feat which is a good reason in a lot of cases to take the race early power spikes and stat allocation in a way you want. Much better on caster classes i might consider the default human class slightly better if you were playing paladin / bard or you needed a lot of mid tier ability scores and maybe 1 high score.

Also early access shield dwarf mages are overpowered currently because of the headband of intellect available at low levels a lack of ability score rolling and a lack of levels present. Ability score rolling would negate alot of the benefits to playing the shield dwarf as levels increased. As you could counter balance it with a feat and the default stat block would be even in alot of cases.

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In conclusion
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There is a lot being overlooked. As noted fire resistance is the most common source of damage in dnd and in the bg3 game outside physical damage itself and if your talking pure stats your weighting an ability score diversity not present currently because not all tiefling races are currently available.