That second post is terrible, terrible, TERRIBLE advice.
There is nothing about onpage SEO that is the "only" important thing. Fact is, they're all important. Why? Because if you have no competition, then you are the competition. And if I come along and see your site in my SERPs with no onpage, I'm going to push you out of my way like a toddler on black Friday.
You need to analyze your competition, check their onpage factors and do AT LEAST that. If you're wanting to come into SERPs with nothing but offpage, that is not only a WEAK strategy, but short term and short sighted as well. (Unless you're just trying to rank some crappy IM site.)
If you want to rank your BUSINESS.. Then you need to solidify it in place, you don't want to risk your business' position because you're lazy and want to take the SERPs with AA ScrapeBox comments. You need to do everything as far as onsite, and to say that title, meta desc (really? Meta desc means NOTHING for SEO!) and content are the only important factors is ridiculous.
- Your title is #1 of course.
- Your URL should be SEO... site.com/category/keyword
- Your images should be ALT! (If not, you just lost a place for keyword!)
- ALL your links should be TITLE! (Again, one more keyword. Whether it's external or menu. ALL!)
- Your navigation should represent the site structure, much like a sitemap.
- Your content should be formatted. (H1, H2, B, I, U.)
- You should have a sitemap.
These are the very basics of onsite SEO and if you think default installing WP is going to take care of even just this, you're sadly mistaken.
Do not skimp on your onsite, how much you're willing to put into onsite is directly related to how much you'll HAVE to put into offsite. If your onsite is 0 and mine is 100, you will require 100X more back links than I will for equal ranking. So if you want to sit around link building all day, ignore onsite, but don't say I didn't warn you when you're wondering why competition with 5% the amount of links as you is outranking your site.
Think of it this way... Say you're a body builder and your competition also is. But he has a gym at his house (onsite) and a membership to another gym (offsite.) You, only have a membership to a gym (offsite.) At home, you lift cans of peas to exercise.
Who is going to HAVE to go to the offsite gym more? You are, because much of his work is done at home. So he only has to come into the gym to achieve things his home gym does not support.. Basically, just to tone up. You have to do EVERYTHING at the offsite gym.
And while you can still beat him at some body builder competition... In order to do it, you spent every single day at the offsite gym. He may have gone in there for a few minutes here and there. However, if he does both (which he can, because having at-home gyms are magic and you can be in 2 places at once).. He will stomp your mudhole.
Onsite is not hard, it's very easy. Be wary some of the advice you receive around here regarding it as well.. For some reason, many people here think that onsite is simply "handled by WP" or is not important. These people mostly do not understand fundamental search engine optimization, they just understand that if you run XRumer and ScrapeBox enough, some magic box in Mountain View will cast a spell on their site and it will rank.
SEO is not magic.. It's very basic logic.