Honestly, there's no such thing as an easiest job while making a hack. It's pretty much subjective: everyone is good at something rather then something else, so it's pretty obvious someone might prefer spriting over scripting, for example, or the other way round. So, nothing is really difficult and nothing is really easy. It all depends on your skills. BTW, not all jobs are listed in the poll.
That said, here are a few things to note:
Scripting: This is actually the easiest thing for me, and it's not as hard as most newbies usually think. Being an intermediate/advanced programmer might help here. Wheter you're good at it or not, you must take care of it as it's the closest thing to the core of hacking, which is ASM. If you think about hacking as a human body, while ASM would be the brain, scripting would be probably represented by the heart. Nowadays, anyway, with XSE and its guide (yeah, you should read it) scripting has become less nightmare-ish than it was when I started working on it. I bet most of you will agree with me. While XSE helps you out though, you still need to learn scripting. Now, learning scripting is often understimated. People usually are happy to learn the basics that's it, maybe even claiming theirselves as master scripters. Sadly, it doesn't really work like that. Scripting is a complex thing you need to handle, it isn't just a mix of words and numbers that will do the magic for you. Therefore you need to understand how everything works and how. I mean, everything: every single command, every single parameter counts. Note I said "complex" and not "complicated". Once you learn scripting properly, it will be as easy as thinking what the script you're working at should do or should not do. You don't really need to remember all the stuff, because you can always press F1 to refresh your memory. Keep in mind the original games are full of working examples, and rather then complaing your wild battle scripts isn't working and demanding a fix you should rather go decompiling a similar script a see what's inside it. Maybe you can learn a thing or two as a bonus. The 3P rule here is: practice, practice and practice again. Oh, and just do me a favor: don't say scripting the hardest thing ever without actually trying. Learning takes time, but it's worth it.
Mapping: Beginners usually starts with mapping, because they all can open AM, load a map and put some tiles here are there. Now, getting a good map... that's a bit different. You need to worry about tilesets, tiles, palettes, connections, and other funny things you are probably aware of. Those things can be understood quite easily, but still that doesn't make you a good mapper. Artistic skills are somewhat required: you can't place houses or trees at random, just to fill the map area.
Spriting: I wonder what's the difference between spriting and OW spriting. Spriting is just spriting, in my opinion. Anyway, spriting requires you being able to draw something, and to color it respecting the game limits (e.g. 15+1 colors). If you can't draw, you're probably getting nowhere. You can still try, of course.
Beta Testing: Next time you're beta testing something, stop for a moment and think how are you doing it. Are you still sure that's beta testing? "Playing the game" isn't beta testing. Beta testing involves the fact you know the hack you're testing as deeply as possible. You need to make sure all the maps are displayed correctly, that every script tile is working as expected, every person is saying the right things at the right time and without typos. To make is short, you need to make sure everything is working as intended. Beta testing takes a lot of time, and if you're lazy or just don't feel spending so much time then you shouldn't be beta testing at all. How come the first beta of my hack had only one little bug? That's because I beta tested it.
