I had the X3 but now own 2 taigs...The biggest difference is Noise,the X3 geared head was incredibly Loud,and couple that with cutting...WOW
Honestly I can do everything on my Taigs that I did with my X3, and the tolerance it holds is much the same...+-.005 or less all day long ,My X3 was used when I bought it though... I have had 1 of my Taigs for about 16 months and it has been used at least 8hrs a day for more than 1/2 of that time and have yet to adjust the brass nuts.....not to say they don't need adjusting i have not seen the need to.
If you go with a Taig get the Gecko driver for it..
I have 8 inches of Y and 17 inches of X on one of mine...all you need is longer Leadscrews and Shim the Headstock out some....you do lose some rigidity but not much
I have used a 1/4 em ramping in to .125 doc at 6 ipm and cut at 9-11 ipm with good results at 5000 rpm if I remember correctly....you could run it faster but it gets pretty loud so this was a nice Medium.....I was pretty much getting same results from my X3 but it was much Louder..LOL
EDIT...oh this was on Alum, for tool changes I use Collars on my tools