i think the pro's would be being able to see under your car better when you have to climb under it to fix everything that breaks because you've spent more money on junk crap instead of good parts.
For cons.. well.. i suppose the biggest con will be being drawn and quartered by the mustand community .
I have a set, the previous owner installed them. Honestly, I have used them all of about 3 times, and that was just for ****s and giggles. Its really a worthless mod and there are much better thngs to spend your money on. However, it is your car and if you want to put them on, more power to ya, get the led ones not the neon tube ones though. Just my $0.02.
Can't tell whether or not you're joking because of the HP question lol but myself at the last car show I attended saw a ton of underglow on classics and personally I thought it looked great on all the oldies.. new muscle.. dont even think about it though
I think he ment with he lose power becuase he using power to run the lights, but neons use hardly anypower. Same with LEDs which I have, look ok but illegal in NY so it's kinda a car show or "look what I have" kinda thing. It's popular with the teenage crowd around here. I think it looks nice if you draw the line there it's on the edge of "ricer" but some can pull it off. Oh and btw everyone knows you only get that extra 25hp if you put the neons on a civic... "If it's got carbon fiber it must be fast"