My father also drives LS' and he was looking at a 745Li to replace his 98, and a customer of his who sold his 99 LS400 for a 750iL and returned it to buy an LS430 told him that the fun of owning a BMW would last him three weeks, then he would want his Lexus back.
My dad bought a brand new 04 LS430 lol
BMW is a great car, the 740i may be one of the best looking sport sedans of all time, but from what I hear from owners and what I see in the reliability ratings, its nowhere near as trouble free a vehicle as an LS. My fiance's father just bought a CPO 740iL and he took it in for the first $350 oil change and they found $1700 worth of suspension work that needed to be done on his "certified" car, not a dollar under warranty,it only has 50,000 miles on it.
Personally to me a BMW is a nice car, but its not anything I'd ever care about owning. Give me a reliable Lexus anyday.