This case is better:
1. 1 backlink with abc.com (Which is PR6)
2. 2 backline with abc.con (Which is PR5)
Because you are getting the higher
PR backlink (6). And for the first case - it doesnt matter weather the
PR of sites linking to you are the same or not. Only
PR value matters and also the outgoing links of the linking site. The bigger
pr of a linking site and the less outgoing links the more
PR juice you will get

[/quote]
How about
1. 1 backlink in abc.com (PR5) + 1 backlink in efg.com(PR4)
2. 2 backlink in abc.com(PR5)