#1
Is the ESP LTD B-15 good for a beginner? I am seeing mostly positive reviews about it, other than there is only 1 pickup. I am a beginner, so do you think this would suit my purpose of playing metal, or should I go with a 4 string like the GSR200? Thanks for any advice.

Here is the bass if you don't know - http://www.guitarcenter.com/ESP-LTD-B-15-5-String-Electric-Bass-Guitar-H71368-i1797722.gc
#2
The B-15 would be a fine bass for a beginner, or for an intermediate player. It is a basic nuts-and-bolts five-string with a P-Bass pickup. It should suit you well.
"Maybe this world is another planet's hell?" - Aldous Huxley
#3
5 strings are better IMO. Most people still prefer 4 strings.

If you find it comfortable and if you ever played guitar so that you can be a judge, take the 5 string.

Else, I would suggest the 4 string.

But maybe learning with a 5 string from the start is not a bad idea.