I'm about to choose between the two firms also. I actually prefer Lightspeed trading software, but when I called their customer service number today, it went unanswered and after many rings, gave a busy signal. WTH? Their "live chat" is unattended and it's regular business hours. I sure hope this doesn't occur if/when I'm having technical difficulties and need help. IB, on the other hand, answered my call in a jif. Anyone know what's going on with Lightspeed lately? It's been a few years since I used it.
I did a comparison between the two a while back and then a friend of mine mentioned Cobra Trading. In comparing the CobraIQ platform vs. IB and the customer service, it was a pretty easy choice. I can talk to Brandon and the guys at Cobra on IM and can always reach them within a ring or two. I like the personal service and they were willing to seriously negotiate commissions to what I needed. I don't know what your major need is, but I found what I wanted in their platform, service and pricing. Feel free to PM me if you want any more info from my search.
Lightspeed had a phone outage earlier today. I have accounts at both IB and Lightspeed. Both have pretty bad customer service but IB is probably worse. Lightspeed is much better platform for equity trading. I like IBs universal account.