I did BOTH courses earlier this year. Back then I thought HTI 2.0 is a second part, so I nailed the first one beforehand and honestly, they kinda complement each other?
2.0 has much more knowledge pumped into it. There are more videos, excersises and it appears more professional overall, however, doing one right after the other, I've noticed that 1.0 touches on some subjects that 2.0 doesn't. I don't remember what it was exactly, but I remember something was missing.
There is also the pdf file with drawings to ink over. 2.0 has less drawings to ink, the choice of drawings is much better though. Some of the drawings included in the 1.0 weren't really teaching you that much, you know? In the 2.0 pdf, you'll find drawings that are much more versatile in terms of linework which is much better to learn from. HOWEVER, the pdf for How To Ink 2.0 has only one version of each drawing, while 1.0 had a couple versions of each one. Finished outline, loose sketch version, stuff like that. I really missed it in the 2.0 since inking over a loose sketch is SOOO much different than just tracing the finished linework which are offered to you in the 2.0.
If you can afford it, I kinda feel like doing both would be the most beneficial since those offer slightly different experienes and cover a few different things. If you can go for only one, 2.0 should be the option though.