As for the cost of spawning an extra shell; I don’t know exactly how much memory that takes, but I am totally sure that it uses a lot less than opening a new tab in Safari!
Try this:
set a to (do shell script "echo $(echo a;echo b;echo c | cat -n)")
It is just something to consider, that the do shell script, collects the output, like you see it in the terminal, it doesn’t necessarily redirect to the next command as a whole, that was the idea of using the sub shell in the first place, to avoid making temporary files for collating and such.
By the way. When you have to do a sudo command, and doesn’t have adminstrative rights on your account, then do shell script with administrator privileges works great!