The Lexus will absolutely be more reliable, I tested a few IS350s before buying my Bimmer, and I just didn't like them. They seemed really cramped (even for someone only 5'10), and the steering was a bit light and twitchy. The driving experience was worth the maintenance trade off to me, and even after 7 years of ownership and close to 70k miles I don't regret my decision.
Oil changes on the BMW are super easy, I can change the oil on it faster than I can my Jeep Wrangler.
Mine is a 2009 328i E90 generation. Reliability really depends on the specific car you are looking at. I would avoid the V8 models, and the early turbo I-6 and turbo 4 cylinder models.
I would consider the naturally aspirated models with the N52 3.0L i-6 found in 2006-2011 325/328/330 models, or for newer than that, the turbo i-6 N55 (2011-2014 335i) and current B58 turbo i-6 found in 2015+ 340i models. The 4 cylinder turbo engines had timing chain issues prior to 2015 when they were revised.
They can be reliable with proper maintenance. Change the oil on time, and have it looked over by a shop yearly if you can't do your own maintenance. I commuted over 100 miles/day in my car for 4 years, and it has been on several 2000+ mile road trips.