For pickups, I personally hate EMG's. Very Compressed sounding, biting highs, and not much variety. I use Bartolini's and I get way more mids, clearer lows, and clear highs. The Bart's bring out more of the character of the bass. EMG's sound like EMG's no matter what bass you put them in.
Adam Duce of Machine Head plays with Bartolini Pickups on his custom Zon 4 String Basses tuned to BEAD and he had a truly massive tone live. Plus, a good chunk of his tone is coming from the SVT Classic Tube amp and Tech 21 PSA-1 for distortion.
I use Active Pickups, coupled with an Active EQ on my Spector Euro 5 string. I don't get tone loss with long cable runs and I have more control over my bass sound.
I am a finger playing dude, but I have learned to use a pick.
I boost in the low mids (220hz) and in the regular mids at 500hz. Sometimes I will drop the low-mids to a flat setting and use the 400-700hz range to get a growly tone going for pick playing.
For amps, I use an Ampeg SVT 2 PRO. Very versatile and awesome growl for metal playing.
I prefer 5 strings because I like the variety of notes I can achieve. Honestly, the G string in MOST metal playing is not too useful. You can always just play further down the neck on the d string. I on the other hand like the g- string and use it a lot. It depends what you want to do. You can find basses with wide string spacing if you need that.