On a purely monetary level, the 3525 sells for a few more dollars than the c1000.
You'd probably be pretty happy with the 3525 for vocals and acoustic guitar, and your friend would do pretty well with two c1000's as overheads. Could be a win/win trade.
Trying it out first is a great idea.
At $150, the 3525 is a pretty good value IMO. I have a c1000 and a 3525. On certain voices the 3525 works better than my 4033! And I still like the way MY voice sounds through a c1000. Of course, it all comes down to the answer that comes up from Harvey and others: "It depends" on what you want/like, and every other variable (sound of the source, the room, rest of the mix, etc.)
In a nutshell, this sounds like a good trade, but the best answer is to try it out in as many situations as possible first.