Not necessarily. From what I have researched, if your are actually an experienced, professional trader, the ability to direct route your orders is considered a must have. Also all things being equal, i.e. being able to use a platform like DAS Trader Pro, they tend to say the fastest execution speed is essential.
That being the case, Lite doesn't have direct routing and will not have the fastest execution speeds. Moreover, depending on how much slower executions are, it is possible that what you gain in free commissions might be lost in slippage. I mean even if your losing just .01 cents per share due to slippage by not having direct routing or access to the fastest routing options, if you by 10,000 shares, that would be a loss of $100, per trade. In comparison, the commissions on 10,000 share would likely be only $40-$50.
Honestly it all comes down to just how much slippage your have with Lite's routing based on what makes IBKR the most money verse Pro's routing based on fastest execution. I am not sure where you might get these sort of statistics at to compare but Pro's routing could actually save you money, even with having to pay commissions.