price is irrelevant. You want a good fabric and a good fit.
Materials and workmanship being the same:
Bad MTM (inexpert tailor) is just as likely to fit poorly as a well made RTW. Either way you'll have to get them altered to fit.
The main allure of MTM is you have more say in the finished product.
Say you want a two button spread collar with rounded french cuffs in a light yellow two ply twill. Likelihood of finding that RTW? fairly low. MTM? no problem. Equal prices, you're going to want MTM.
White, barrel cuff, fake MOP buttons in a 2 ply twill with a single button spread collar? Not hard to find. You may be able to afford a RTW shirt that is higher quality than a MTM shirt of equal price, and spend 20 bucks gettting it altered to a near perfect fit. For something like that RTW is a far better option.
Really depends on what you want. Sorry if that wasn't much help.
+1. It's all dependent on fit. Expensive RTW that fits perfectly can't be beat.
But you see tweed at night would not be overdressing to the forum. It would be lazy and sloppy and possibly gauche in a devil may care way on the right person.
Just wondering if tweed would be too twee?
Agreed, tweed would be too informal for a dinner party. But as the newbie consequently pointed out, most will think you are being over dresses, so go for it. You can secretly snicker to yourself, in regards to your slovenly appearance