Obviously every player makes errors, but numerous of them have been Beltre just making stupid mistakes once he gets the ball. Anyway, my point is: Beltre is going to make more errors then most third basemen due the fact that he gets to more balls then most 3rd basemen. Lowell is not an upgrade defensively, if you want Beltre gone at least say for a good defensive 3rd basemen. (Note not directed at anyone particular with that comment but I have seen numerous people begging for Lowell to start over Beltre).
Since you watch the games, you honestly cant see how much more range Beltre has then Lowell? Wether you believe UZR is a reliable stat or not, you can tell just by watching the games that Beltre's range is 10x better then Lowell. Beltre is the better defender and it will show as the season progresses. Lowell has no hope of getting better defensively because he is old and never really was very mobile, those hip surgeries have killed his mobility, therefore limiting his range.
If UZR is not a reliable stat, then why is Fielding%? Fielding% can be even more misleading then UZR. According to fielding%, Mike Lowell is best fielding third basemen of all time. You know why? It doesn't factor in range. Just in the past few years Lowell has look absolutely terrible defensively, while Beltre has looked fantastic, but you cant tell that by fielding%. However, with UZR you can.
UZR is a reliable stat, you just don't understand it.