In a word, "yes", both methods will give you a sound, functional, repair.
I've been running the same NGK twist-on splice for the past 14 years and north of 22,000 miles on my daily rider. It works as intended, no problems, and...is fugly.
The soldered splice method is better, imho. It's just more work and a little tricky around the edges. You have to leave enough exposed wire length so that the solder will flow, without melting the wire insulation. That means a good ~0.500" that has to be filled-in afterward. The inner core of the factory insulation you'll have to remove to expose the copper strands is a good base layer because it's rigid, ideal for a strain relief. The outer layer oftentimes will be too thick to reuse, the soldered splice is ~twice as thick as the individual copper conductor segments. All the matters, at this point, is getting enough polymer wrapped
tightly around the inner layer to fill-in what remains of the gap and eliminate the stress riser that would otherwise exist. IOW, you're replacing the external structure so as to replicate the original, unbroken, lead length as it was pre-splice. My preference is self-fusing silicone tape. However, electrical tape is fine...you could even use silicone RTV, it sets-up firmly enough. The shrink tube is key; it seals the joint and gives structural bracing. It's also not highly visible.
There's nothing stopping anyone from adding a final layer of rubber hose or thick plastic sheathing to the exposed section of HT lead. Most of the early bikes came from Honda like this. Talk about having your cake and eating it...
