Q ab. Hard Drive upgrade; PATA/SATA, S.M.A.R.T., HDD Controler

I have a few questions about replacement hard drives for my PowerBook G4 12" 1.0 GHz DVI. (I am also going to upgrade the hard drive in my wife's Powerbook G4 15" 1.33 GHz Combodrive, but I think the questions/answers below will apply to both. I'll just deal with my 12" for ease here.)

I have read Apple's specifications and searched all over to find detailed information about ATA ratings and compatibility, and I'm still in the dark about a few things. I'm interested in a 160GB or a 250GB internal drive to replace my 80GB (which did come standard as an optional feature, although this is my second 80GB--I burned the first one before my Applecare expired), and I'm looking at the following drives, for instance:

HITACHI Travelstar 5K160 HTS541616J9AT00 (0A28419) 160GB 5400 RPM 8MB Cache ATA-6 Notebook Hard Drive - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16822146200

Western Digital Scorpio WD2500BEVE 250GB 5400 RPM 8MB Cache ATA-6 Notebook Hard Drive - OEM
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136159

Questions:

1. HDD Controller limit to internal drive capacity: I've read that older powerbooks (whatever this means, it wasn't specified) may have a 128GB limit, supposedly meaning that the HDD controller will only recognize 128GB on an internal drive. Anyone know if this is true? How do I find out? It isn't published on Apple's spec page for my machine. And, if such a limit does exist for my machine, can I install a 160 GB and get the full 128GB? (b/c a 120GB will only give me 100+ usable after all.) Will the fact that the drive is lager than the total recognizable amount mess up the cataloging, data retrieval, reliability, stability...?

2. ATA-100 vs. ATA-6 vs. ATA-7 vs. PATA vs SATA. My present 80GB TOSHIBA MK8025GAS just says ATA in the System Profiler "Protocol" field for the ATA drive. I presume that the SATA is a later, more recent, non-backwards-compatible format/pin configuration/?. I presume the 100 refers to the 100mb/s data transfer rate, which is what the Apple specifications have for my machine. The drives I am looking at, by and large, are rated at 100mb/s. They all have other specifications, however (ATA-6, ATA-7), and I am hoping to hear that they do NOT refer to pin configuration differences.

-Q- will PATA and SATA drives both fit my machine, or does the "Ultra ATA/100 hard drive" listed in the Apple Specs for my machine mean that the pin configuration/compatibility will only work with PATA drives? Thus, Is Parallel ATA what I have and need?!?! Will a faster SATA drive work in my machine? Would I be able to swap it out into a MacBook Pro when I upgrade next year? (i.e. are SATA drives &/or boards backwards compatible with PATA drives? And are PATA drives &/or boards forward compatible?)

3. S.M.A.R.T. verification capability. I am unclear as to whether this capability is essential and which drives provide it. Some information states that Hitachi Travelstar drives DO support S.M.A.R.T. verification, but such is not listed on their information about the drives. My present 80GB Toshiba DOES have this capability, so System Profiler says. Before my previous drive failed, SMART notification may have saved me (though it's unclear if it actually made any difference--it's just notification, after all, right?), alerting me that the drive was failing and thus giving me enough time to get the last bit of un-backed-up data off the drive before it died altogether. (This is a presumption based on changing S.M.A.R.T. status notifications in System Profiler and from Disk Utility Repair Disk reports). In fact, however, I don't really know what SMART verification is, and thus I don't know how important it is.

-Q- How important is S.M.A.R.T. verification capability? And what is it really?

-Q- which manufactures support it?

Many, many thanks for any insight.