After seeing a lot of discussion on this thread, I tried to do some calculations to see who can hold more stuff on the inventory and who would win on a battle:
(All the information and numbers used here were taken from both games Gamepedia wiki)
Let's start with the inventory. Steve's inventory has 27 storage slots + 9 hotkeys slots + 4 armor slots, While the Terrarian inventory has 40 storage slots + 10 hotbar slots + 4 coin slots + 4 ammo slots + 1 trash slot + 3 clothing slots + 8 social slots + 8 dye slots + 5 accessories slots.
We'll scrap the Steve's armor slots, and the Terrarian's coin, ammo, clothing, social, dye and accessories slots. This gives us a total of 36 slots for Steve and a total of 51 for the Terrarian
The material we will use to measure how much one can carry is Gold, which can be stacked up to 64 for Steve, and up to 999 for a Terrarian, meaning that Steve can carry 2,304 gold blocks, while a Terrarian will carry 50,949 gold ore ( as ores in Terraria are pretty much a square of said ore, they can be compared to MC's gold blocks)
Now let's see how much a gold block/ore weighs:
Starting with MC, each block is 1m³ , So discovering how much it weighs is simple:
1 * 19,300
(Gold's value of kg/m³) = 19,300
19,300 * 2304 = 44,467,200
Steve can carry 44,467,200 kg of Gold. Great.
Now for our Terrarian friends:
One block is 2ft tall
(2ft = 0.60960m) , So each block is 1.2192m². There's no way to discover the block's volume, as Terraria is viewed from a 2D perpective, meaning that the block's width could range from nothing to the infinite, So this time we'll just use X instead of any value.
Each Terraria block is X1.2192m³.
X1.2192 * 19,300 = X23,530.56
X23,530.56 * 50,949 = X1,198,858,501.44
When we use Gold as a common measure between both worlds, it sounds like a Terrarian can carry a lot more stuff than Steve, But in reality, there's no actual way of knowing wether this is true or not, because we don't have all the values of a Terrarian block. Again, a Terrarian could be carrying both the value of the infinite or nothing.
Conclusion: If a Terrarian Block width is ≥ 1m, a Terrarian can relatively carry more than Steve.
Now for a combat between Steve and a Terrarian:
If both went bare handed, Steve would win, as a Terrarian can do nothing without Tools/Weapons.
But what about other situations? Could a Terrarian win? I think so, Because Terrarians seem to have a lot more belic power than anything we see on MC, with their arsenal ranging from swords to lasers.
Let's see what could really happen:
First, We have to discover how much health Steve has in Terrarian terms.
From MC wiki:
''The basic measure of health is one hit point 1 (). One heart 2 () is also commonly used when talking about health.''
So Steve has 20hp.
Each Terrarian begins its journey with 5 Hearts, each one having 20 hp, So Terrarians have 100hp.
On this hipothetical scenario, We have Steve Wearing a full diamond armor and sporting a Diamond Sword, While our Terrarian is in Full Platinum Gear. They will always hit each other, they dont have any kind of buff, enchantment or reforging on their equipment, And no critical hits will happen.
A diamond Sword (MC) can deal 8
damage, which is 16 hp per hit.
A Platinum Broadsword (Terraria) can deal 15 damage per hit.
a diamond armor (Helmet, Chestplate, Leggings, Boots) (MC) Will give a total of 10
(+20hp)
Whereas a Platinum armor will give 16 Defense + 4 def from set bonus (20 def)
Steve's diamond sword's damage is smaller than the Platinum Armor's defense, And by Terrarian Logics, it will deal 1 dmg per hit. Our Terrarian has 100hp, so Steve will have to hit him 100 times to kill him.
The Terrarian's platinum Sword Deals 15 damage per hit, and to deplete both Steve's Armor and Health the Terrarian will need to hit him 3 times (45 damage total)
Conclusion: By following my Minecraftian Hearts to Terrarian Hearts conversion logic, The Terrarian would easily win the situation depicted above