I drove a 2005 Titan SE 4x4 CrewCab for 3 years, so I think I can give you some input. During that time it was my daily driver, I put almost 50k miles on it. It was a new vehicle, so I can't compare reliability to my 10 year old X5, but my rear differential was replaced under warranty at around 30k when it started to clunk and that was it.

Size - obviously it's much larger than even the newest X5s. It can be difficult to park if you communte to urban areas, however driving normally was never a problem as visibility is great and most people get the hell out of the way when they see you coming.

Comfort - it was unquestionably more comfortable for both front and rear passengers - you were never confined by legroom or hiproom etc. The ride is softer than the X5.

Speed - it was faster in a straight line than my X5 4.4i, that's for sure. I ran mine down a 1/4 mile a few times and clocked a 14.9, which is about on par with a 4.6is.

Handling - remember, handling isn't very high on the priority list for pick-up trucks. It handled like a boat, you'd never want to take an on-ramp at speed unless you were trying to kill yourself. You really can't compare it to an X5 because that's a night and day difference. That being said, the Titan handled well for it's size and weight.

Utility - the Titan can probably fit more in it's rear cab that the X5 can in it's trunk + rear seats... it's that big. The bed has it's obvious uses as well.

Luxury - as mentioned above, the Titan lacks this no matter what trim level you get. The materials and design are not up to par with BMW. Period.

Overall, I really like the Titan and I thought it was great for a daily driven full-size pickup. I would definitely buy one again. I moved into a city and found it impractical, so I sold it and ended up with my X5. I enjoy the X5 much more around here as I often have to parallel park or squeeze into small parking spots. Also the handling/steering feedback of the X5 is on a different level which I had missed from previous performance-type vehicles I had driven.

Hope this helps!

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2002 BMW X5 4.4i