The big microfibre cloths are first rate! Easily superior to scrim, but they are one of those tools you have in your armoury, they don't replace the scrim in every area.
I think both scrim and microfibre easily replace the traditional leather though, both are longer lasting and harder wearing.
For wet work, such as sills and frames I prefer scrim, scrim can be wrung out and still be great to use.
Microfibre is better when fresh and fairly dry, but once wet and then wrung out it just isn't as good as scrim.
So I have both scrim and microfibre. microfibre for the fussy buffing work, and scrim for the more general tasks.
The big microfibre cloths have really come down in price now, they are only a little more expensive than scrim.
Ian