If it's three years old, I'd opt for a softmod. There are plus and minus points for either school of thought (soft/hard). Softmod = free. Hardmod = $$$. You wouldn't be able to use a USB HD via hardmod (the ones that do/can support it would be the Sundriver or WODE; I'm not sure if they come with a drive or not --- no experience in them; others may be able to elaborate).
Softmod if done via wiihacks guides (you got the links in your intro post) are pretty robust and should keep you playing without issue. The important things to remember: Priiloader isn't an "option" but rather necessity. If your Wii is 3 years old, there's a fair chance you can get BootMii installed as boot2. Making a NAND backup is also imperative. With these things mentioned, you'd be pretty bulletproof.
Hardmods cost money. You generally have to accept updates. 4.2 Wiis and up (yours for example) can't play out of region games (softmods can). Hardmods you can accept updates for the most part without issue or certainly with less issues. Discs for most hardmods spin @ 3X on both soft and hard mods (a few of the latter will support the full 6X but they are the exceptions). USB HD in conjunction with softmod will load faster than any disc-based game, whether hard or softmodded.