NA-t bang for buck is and always will be the better option. It's just always ended up that way. Hundreds of cheap XS turbos with success rates. 400hp within reach, time and time again.
HOWEVER. I'm NA-t, would I advise it? God no! Unless auto, that's not so bad. But manual, hell no. Unless you can risk the spend on another gearbox.
Don't do it. You'll never be happy with 400hp, and to get to 500/600hp you're end up spending way more than going TT in the first place.
But the main the biggest reason not to go NA-t, is the w58 is a gamble on 400hp of power. Lots of opinions, lots of success and failures. But 400hp, turbo, is a gamble. Fact. If that pops at today's prices you're looking at a mega spend out for the SAME as what you already had, but exactly the SAME gamble on a NEW gearbox (unless you fork out EVEN MORE to upgrade further!).
NA-t is not something I'd advise due to w58, that's an expensive risk. Swap a GTE engine and you still have a w58 which can pop at any moment.