Well ... to shorten the discussion right from the start linear guide rails are better
. They are overall more sturdy, have fixing points every couple centimeters (linear guide rails should normaly be mount on a sturdy frame instead of being a part of the frame themself), twist resistant and most important quality controled (also preloaded till praktical zero play) and normed.
What makes the design from the CR-10 relatively reliable are the use of rigid aluminium profiles (compared to acrylic, thin sheet metal or wood) and ability to reduce the play of the "bearing assemblies". Yes you heared right you may not noticed yet that you can adjust any "bearing assembly on the CR-10 to reduce play, to do that you tightenn these (sorry I don't know the right name) "counter nut's" between the actual ballbearing and the aluminium profile (you will notice any bearing assembly on the CR-10 use it on 1 side the other is fixed with a round spacer, I will make pictures later).
That together with the fact that the linear guide system is the frame at the same time has also the profit of a very cheap package for the whole printer. Even though it uses only aluminium extrusion profiles -which are not meant for precision guidance- the printer moves fairly acurate for the price and are supirior to many other frames (acrylic, wood or thin and possibly bad engineered sheet metal frames) you may can also imagine that 20x20 or 20x40 profiles are less prone to sag and bent compared to 8 or 10 mm linear rods.
But the CR-10 has it's flaws (these are in no particular order) some of these I would also critical (1. 4. and 5.) ....
1. the heatbed is most likely not cast and milled aluminium also pretty thin and takes very long to heat up since it's so low powered (I'm now able to heat up till 105°C in 40 min ... after adding melamin foam isulation)
2. the PSU is a cheap unit only 330W(even thought the cablemanagement is executed well), that with a 300x300 mm heated bed
3. electronics is based on a Melzi S(?) admittedly with better screw terminals, ecternal mosfets with own cooling, but the super cheap chinese Alegro soldered on drivers onboard (dead driver = most likely new electronics)
4. solder joints on the heatbed will brake, no stress relief I would also like some earth on the bed itself (at least if it get an upgrade aka mains powerd or 24V with 350+ W power)
5. the leadscrew/flexible coupler can be bent on stock the motor and moveable bearing isn't always parallel to the z axis, some people added a washer between the motor mount and z-axis to fix that (I need a new coupler and well redo the motor mount)
(6.) a moveable z-endstop would be nice and could be archieved easily
(7.) many people reported about a uneven glas plate on their kit (mine is fine)
EDIT: some spelling and sentence construction I'm sure I could correct more