(I've owned and used Powerbooks and MacBooks from the beginning -- I had a Powerbook 100, the 16 mhz 68000 with a lead acid battery. Used a 140 and 170 of that era as well. And a Duo230, and a 5300, and a Duo 2300, Tibook G4, White x86 Macbook, 2012 era Air and MBP, 2015 MBPs, a work 2017 MBP, Last x86 Air, M1 Air).
Early machines had a lot of flex. The hinges creaked. The trackball gummed up. Some of their keyboards were good (the 140 and 170 especially had _really_ nice mechanical keyboards, and a good trackball as well). And some of the keyboards were mushy goo (the Duos, and the Tibook to a lesser extent. Basically the low point till the 2016 MBP). Despite the magnesium frames in the duo, the whole computer could flex enough that the battery would disconnect while in use. Also, the Duos were a royal pain to repair -- I remmeber an hour or more to disassemble to get to one little piece in the back that needed replaced -- I think it was a serial port.
The spring loaded keyboard on the G4 (and the toilet seat ibooks) was great from a maintenance POV, because you could get into the innards really easily to replace memory, drives, etc. But the keyboards on the unibody are soooo much better.
The Tibook was an inflection point where the machines started lasting me more than a couple of years. Some of that was probably usage patterns (having a desktop for the heavy lifting), and some was build quality (and possibly, some was buying a top of the line machine for the first time). But even then, the Tibook has wear that the newer machines just don't show -- the paint on the frame rubbed/chipped off at the wrist rests. The body over the dvd would flex and rub on the spinning disk. The 2012 Air was basically the platonic ideal of a laptop at the time, and it worked in its form for 5+ years, only really being put out to pasture when Xcode demanded too much from it.
The unibody MBP was probably the closest to what you'd expect from a modular MBP these days, but it took a lot more futzing because of it. The SATA drive cable rubs on the frame due to flex, giving it a lifespan of a few years, even for pampered machines.
The unibody and shift away from moving parts really did do wonders for Mac laptop durability in day to day usage.
This naturally affects the conditions these machines are available in on the used market. Any of the pre-TiBook plastic models are likely to have cracked plastic with bits that have chipped off due to growing brittle with age. PowerBook G3s are likely to have their exteriors scratched up. Fruit flavored iBooks commonly have parts missing. As you noted, TiBooks have big problems with paint chipping and had bad hinges.
Once you get into the aluminum models things improve quite a lot… the PowerBook G4s and MacBook Pro’s, both pre and post unibody can easily be found in great condition. The counterpart white plastic iBook G3s/G4s and MacBooks also fared better, but are sometimes subject to yellowing. These generally don’t have mechanical issues and usually just need to have their spinning rust swapped out for an SSD and a thermal paste change to get them running nicely again.
That said, the pre-unibody alu Powerbooks and white plastic iBooks/MacBooks are a pain in the butt to work on. So many screws. If one doesn’t have much patience for that kind of thing and doesn’t explicitly need PowerPC one of the unibody MBPs with at least a Core 2 Duo is a no brainer when selecting an old Mac to tinker with.
The power connectors got better -- from the standard DC barrel (weak) to a hybrid RCA/headphone jack thingy (stout, but rough on the cord) to the magsafe, where now it's just the cables that go bad.
The ports got better too -- I killed a couple of the old RS422 serial ports on the duo (printer/modem port), but none of the USBs have ever gotten knocked off the board. At least with the duo, the dock connector had a big physical latch separate from the massive electrical connector.
Ahh yes how could I forget MagSafe. That was a huge improvement.
I’ve seen some people modding old thinkpads to use USB-C for charging instead of those old barrel connectors that love to get loose over time and break. I wonder how practical it would be to do that for pre-MagSafe PowerBooks/MacBooks.
(I've owned and used Powerbooks and MacBooks from the beginning -- I had a Powerbook 100, the 16 mhz 68000 with a lead acid battery. Used a 140 and 170 of that era as well. And a Duo230, and a 5300, and a Duo 2300, Tibook G4, White x86 Macbook, 2012 era Air and MBP, 2015 MBPs, a work 2017 MBP, Last x86 Air, M1 Air).
Early machines had a lot of flex. The hinges creaked. The trackball gummed up. Some of their keyboards were good (the 140 and 170 especially had _really_ nice mechanical keyboards, and a good trackball as well). And some of the keyboards were mushy goo (the Duos, and the Tibook to a lesser extent. Basically the low point till the 2016 MBP). Despite the magnesium frames in the duo, the whole computer could flex enough that the battery would disconnect while in use. Also, the Duos were a royal pain to repair -- I remmeber an hour or more to disassemble to get to one little piece in the back that needed replaced -- I think it was a serial port.
The spring loaded keyboard on the G4 (and the toilet seat ibooks) was great from a maintenance POV, because you could get into the innards really easily to replace memory, drives, etc. But the keyboards on the unibody are soooo much better.
The Tibook was an inflection point where the machines started lasting me more than a couple of years. Some of that was probably usage patterns (having a desktop for the heavy lifting), and some was build quality (and possibly, some was buying a top of the line machine for the first time). But even then, the Tibook has wear that the newer machines just don't show -- the paint on the frame rubbed/chipped off at the wrist rests. The body over the dvd would flex and rub on the spinning disk. The 2012 Air was basically the platonic ideal of a laptop at the time, and it worked in its form for 5+ years, only really being put out to pasture when Xcode demanded too much from it.
The unibody MBP was probably the closest to what you'd expect from a modular MBP these days, but it took a lot more futzing because of it. The SATA drive cable rubs on the frame due to flex, giving it a lifespan of a few years, even for pampered machines.