Wow. Just wow guys. Lots of speculative misinformation here.
Here's some hard FACTS - based on years of
GW and Gunpla experience.
1. Plastic Type
Games Workshop uses a softer, more impact resistant plastic. -edit- this is why you scrape off the mold lines. Typical panel thickness is 2-3mm on Imperial kits, and 1-2mm on curvy kits like Eldar kits. Thin parts detail parts are becoming more common. Given the look of the new Necrons,
GW looks like they're finished with the clear plastic experiment outside of canopies.
Bandai uses a harder less impact resistant plastic. -edit- if you try and scrape the mold lines on this plastic, you will only scratch it. Hobby files are required for these kits. This alows for sharper details. Typical panel thickness is usually 1mm. Bandai has a "system injection" system which alows for multiple on-sprue colours including clear bits. Extensive use of polycaps for joints.
2. Detail Level
Games Workshop uses heavy details such as oversized rivets and skulls. While some kits have much improved detail, many are relatively featureless - i.e. Monolith, Rhino (and most
SM vehicles), Eldar and
DE vehicles. This is due to their aesthetic and not due to any process.
Gundam kits come in 4 major detail levels.
At level 1 (
HG 1/144 scale) they have basic panel lines, vents, verniers and engines. Basic articulation
At level 2 (
HG 1/100 scale) they have all of the above including additional panel lines articulated armor, additional articulation, weapons, option parts
At level 3 (
MG) they have all of the above including additional panel lines removable armor panels, articulated under skeleton, screw reinforced underconstruction, articulated engines, verniers and sensors.
At level 4 (
PG 1/60 scale) they have all of the above including more of everything included at
MG level.
Some Gundam kits look devoid of detail. This is because they are based off old legacy 70's designs and not due to limitation in process. If anything, Bandai's injection system alows for finer panel lines.
From my experience,
GW detail level is about the same as Bandai 1/144 level.

1/144 Wing Gundam Zero (800 Yen)
3. Durability
I wouldn't say that Gundam kits are not durable. The fact that each built up assembly is smaller (and denser) due to the internal peg and polycap system - each sub system is pretty durable. In fact, I would put Gundam durability above
GW kits like the landspeeder, and
DE vehicles. Sure, your Gundam will shatter into its component pieces if you drop it, but it is only a matter of putting the polycap joins back together again. As for not holding up to play - I can refute this from experience. In my experience, a standard 1/100 kit can stand up to play - where the only downside is a loosening of the polycap joins - usually in the hip ball joints. Most builders don't play with them for this reason, but this is a purely individual choice.
4. Miscelany
Bandai also makes and sells these for 6800 yen. The engineering involved to make a fully artuclated, transformable, three mode model kit makes
GW's kits look stone age.