I think both have their advantages and drawbacks.
Tarantula are exceedingly, almost comically fragile. If you sneeze toward one they basically explode. God forfend you drop or rattle one.
I’d go for the T-Rex just for reasons of durability. I’m too clumsy to live as a tarantula.
If you woke up tomorrow and you were a t-rex you’d be in a zoo or something by noon
That’s not great but the guy above you reckons you’d die quickly, due to not having enough air.
After a night of fitful dreams, Gregor Samsa awoke in his bed transformed entirely into a gigantic Tyrannosaurus rex. His sister had him in a zoo or something by noon.
The end?
Wait, is this an interview?
I’d be… uh… a t-rex… because, uh… I’m not afraid to… uh… take initiative?
We’ll call you.
That’s a tough one… if I choose T-rex, do I live in the cretaceous, or in the present ? do I roam free, or am I encaged ? am I fed goats, or lawyers ?
Same questions regarding the Tarantula
If it’s T-Rex in present day no thank you. You would die a painful quick death due to not having enough air to breath even at sea level.
Oxygen levels wouldn’t be a factor. The “need high oxygen levels for large size” only applies to invertebrates with very simple breathing systems.
If trex had similar type of lungs as modern birds, they would do just fine. Bird lungs are super efficient (much better than mammals’ puny blind sack lungs) that enable them to fly at high altitudes.
Tarantula, because I have arachnophobia - why be anything other than what scares me the most?