For low- or medium-comp keywords, web2.0s can do the job. Expired work better, of course, but if you have a bit of patience, you can make some great new web 2.0s which can work great, as you build them with one goal in mind. But they take time to build, pump, and then transfer the juice. Personally, I mix them.
They cost me nothing but some half-automated time.
That being said, good PBNs are way more powerful than web 2.0s. But for a newbie, it's OK to start with web2.0s and learn along the way. That should get you some experience, which will later come in handy when building PBNs or buying PBN links.
I've had some pages ranking nicely with 30+ links/posts on expired web2.0s. However, just 5 PBN links to a similar page (kw difficulty, Number of searches, etc) did better and was more resilient to drop in SERP later on - easier to maintain ranking.