I recently purchase an X5 and went through the same decision. I finally went for the X5 because it had the linear ways. I have been very happy with my decision. I would have eventually went with these even had I purchased the X4 but decided to go with a complete engineered setup. I am impressed with the fit and finish of this machine and especially how well the wiring was done. I bought my with the stand and it makes a very nice package to which I have built an enclosure using the shipping crate material. I am in Mongolia and I am finding that it is difficult to get things here and I have had to make do with materials I have on hand.
The only issue I have had is the step drive quite working but Syil was quick to send me a new one and I am back up and running. I have not had a lot of time to use the machine but it is very smooth and I am getting about 150ips rapids with 100 acceleration on all 3 axis.
Happy to answer any questions you might have.