I now understand it does not matter for safety reasons to transfer USDT via one or the other network.
Behind the curtains one coin can be stored on different addresses at Binance. You as user do not really have an insight in this (although you can check some historical data).
You can use block explorers to work out where your funds went too. You just need to put in the address you sent funds from and keep clicking until you get to the exchanges address (often one that holds a lot of funds but sometimes one that has lots of inputs and outputs - like a wallet that's actively processing deposits and withdrawals).
The safety of the coin itself is an aspect of how USDT works in general. USDT is (should) backed by real USD, so a failure within one network should be covered, in theory at least.
According to the "Transparency" page on Tether.to there is currently even more USDT on the Tron network than on Ethereum. So if popularity would impact risk in a positive way, this is a good thing.
The security of usdt and tron gets tested quite a lot by its existence on defi platforms (like exchanges/liquidity pools).
If it were insecure, it wouldn't have lasted this long. If it didn't have a full reserve it probably would have though as people will mostly assume it's 1:1 and an attacker probably wouldn't have enough money to compete with usdt's fund even if they only had a few % of a reserve (some coins have taken 20% to reach their peg with bad liquidity).
Yet I highly doubt if this safety aspect applies to all crypto currencies that lives on different networks, as I wonder if all these crypto currencies have the same intricate financial/safety mechanisms.
Most stablecoins suffer from it.
Lots of tokens suffer from having bad code and vulnerabilities in their smart contracts or dapps. Most actual coins don't suffer as many of these losses as they provide more basic functions (like bitcoin and ethereum).
