*They have the safest bases that prevent infantry and light vehicle base-rushes.
*No-tech AT guns so you never get rushed with vehicles without an answer
*AT gun with retreat - much less likely to lose them if you missmacro
*No weapon drops for mainline inf so you are not feeding the enemy your weapons if you lose squads
*Free-ish weapon and nade unlocks (baked into tech and cheaper overall)
*Strong nondoc elite inf lategame that can replace volks losses (less punishing to lose inf)
*Extra support and protection if you build shwere outside of base sector
*Nondoc super heavy tank that can be build even if you lose strutures
Is there a faction that is better or similarly good for a new player?
I'd probably put OKW pretty high on "hard to learn" list, mostly because they have so many strange and unique "features" that don't carry over to any other faction. In a vacuum, sure, they're fairly straightforward to learn; but as soon as a new player tries a different faction, they'll need to learn a lot more. Regarding your points:
1. Only if you're playing 1v1, otherwise you'll probably get OST bunkers. Also, relying on base defenses isn't a great plan, and realistically, base-rushes aren't all that common.
2. While Raks are more forgiving, it can also teach you 'not-ideal' ATG usage (pushing too far, etc.) and reliance on camo, which no other ATGs have (non-doc). I also find they're frustratingly inaccurate.
3. Yes, but you also can't pickup weapon drops on mainlines once you get STGs, so it's sort of a trade-off.
4. This is the same on OST.
5. They're strong, but tricky to use; they'll show up quite squishy and be competing with Vet 2 or 3 upgraded infantry, which will force them to retreat quite quickly if you're not careful. Once they get vet, yes, they're very powerful.
6. I find that the KT is a bit of a "beginners trap"; the only time to build it is if you're winning by an incredible margin already. Otherwise, you've spent an incredible amount of resources on a single, slow, tank that can be countered (or at least, held off) quite easily by pairs of TDs. I find that it's much better to get a JP4 and P4, or really any other combination of stock tanks.
Overall, I'd recommend learning OST first. They have a linear tech order (unlike OKW) which means you'll never miss standard units, simple base healing, and a generally strong roster of units. Except for LV rushes, they generally don't have a downside for beginner players, unless the player has trouble preserving squads. Learning OST will also tech the fundamentals of every other faction in the game, which OKW might not.