Hey guys,

In one of my songs I have the following riff/lick/something with a tempo of 120bpm:

Bearing in mind that all the notes in this part are supposed to ring out into one another... with the picking hand, should the motion be the same as the sweep picking motion, or should each string be picked individually? If individually would it be better to pick them with all downstrokes or a combination of downstrokes and upstrokes?

Also, should the picking technique change depending on the tempo? If so, how?

Let yourself be guided by the tone you get from every way you play it. For me it would be alternate picking or a random pattern of separate strokes.

Obviously both picking and fingering require adjustment at higher speed.
You should play whatever is most comfortable, unless the song requires a specific tone.
Personally I always seperately pick in one direction slow arps such as this. If it were faster, like 200 bpm. I would alternate pick it.

Your focus should be the sound you're getting though. Because we're playing music :P
Thanks guys, I hadn't thought of alternate picking it. So I tried it and it sounded very nice and clean, I'll definitely use that for a fair few other arpeggios. In this case I found that after comparing them, doing a sweep picking motion with my right hand but still letting the notes ring out into each other sounds best for this one and makes the notes blend in nicely due to the rhythm guitar behind it. But for some of my other arpeggios the alt-picking seems to work well. Thanks a million for the tip guys. >: D
Alternate picking that = playing guitar on hard mode. Forget that.
Logical picking means pushing your pick towards the NEXT string you're going towards. If i'm picking a note on my G string followed by a note on the D string, i will use an upstroke on the G. Why wouldn't i use a down? because that puts my pick BELOW the g string, even further away from my D.
So, with that in mind, pick the first four measures like this: down, down, down, down, up, up, up, up. The first upstroke, the one on the high E, will feel a little weird... but its all in the name of getting your pick moving towards the NEXT string (the b string).
The last 2 measures should be down, down, up, up, down, up. Again, its all in the name of keeping your pick moving TOWARDS its next target. That's the most important thing you can ever learn about picking stuff like this.
Another disciple of economy. Why would you use alternate picking if the motion is less logical/economic? Because you favor the sound.
Nah, I'm a diehard alternate picker. But there are certain times where it just makes no sense to alternate pick through something when a series of down or upstrokes would be so much more efficient.
Good for you, but again, your reasons should always be the sound you want, every other reason has to subordinate unless of course skill cap complicates the situation.