We are always trying compare player A with player B.
Nobody disagree that the offensive aspect of evaluation is easier to quantify. I like OPS a lot and use it often, but almost everyone agrees that OBP is more important than SLG%. I'd prefer an OPS type stat that was maybe 60% OBP + 40% SLG.
Base running is also part of an offensive calculation and it goes beyond SB and CS. I do think oWAR does a pretty good job separating the values and then combining them into one number.
Obviously defense has always been much harder to quantify. It's probably impossible without some major technological breakthrough. Fldg% is woefully inadequate, yet many posters still rely on it to make judgments. Home field scorekeepers are highly subjective, but that's not even the major issue with using fldg% as a major factor in determining defensive value. To me, range, especially at SS, CF and to some extent 2B, RF and LF can and often is much more important than how many routine plays you complete. I'll use the SS position, because, to me, it is the most important defensive position on the field beyond maybe the catcher position. The difference in errors between the top 8 innings SSs last year is this:
1405 Andrus 22
1360 Bogey 11
1359 Desmond 27
1350 Ramirez 16
1336 Aybar 17
1330 Gregorious 13
1307 A Escobar 13
1305 Semien 35
The disparity between 11 and 35 is significant. 25 errors over 150 games is one more error every 6 games. The widest fldg% disparity is .037 (.984-.947).
Some very significant disparities there, but now let's look at total plays made- something many baseball fans rarely look at: (PO + A)
Andrus 764
Bogey 665
Desmond 643
Ramirez 666
E Aybar 603
Gregorious 607
A Escobar 635
M Semien 621
Let's look at the differences between Gregoriious and Elvis Andrus. Gregorious has a better fldg% by .007, but can anyone really with a straight face say that makes him better than Andrus? Andrus made 157 more plays than Gregorious! Maybe some of that can be attributed to their pitching staffs-- how many ks they have/how many ground balls to SS they allow, but clearly more is needed than just fldg%. Andrus had 9 more errors, so he must be worse, right?
RF/9 (range factor over 9 innings) tried to address this, but it ignored how many balls were hit to the SS position. RF/9 does have some value, and when using it with fldg% one is improving his point of reference, but UZR/150 attempts to address the issue of how many balls are actually hit to a player vs how many they make. Certainly, there are flaws as some balls are hit harder or farther away from the fielder than others. Some balls are easy, some are hard, some are near impossible and some are impossible. UZR/150 tries to distinguish between all these types, but is rated by people who are flawed. I get that. There must be differences between some raters, but they do try to mix them up and move them around, so over a full season or two or three, it should all "even out" to some extent. None the less, the metric is seriously flawed. However, the question is really about the extent of the flaws vs the extent of the flaws of people using seriously unbalanced personal observations combined with fldg% and RF/9. Which is worse?
It's my position that UZR/150 over a large sample size is better than the eye test + using rudimentary fldg stats.
Let's go back to Gregorious vs Andrus. Andrus played in 75 more innings, so that has to be factored in. Without knowing how many balls were hit to the SSs, I'd say Andrus is clearly the better SS despite making more errors. I'd say the 157 more plays outweighs the 9 more errors, but I'd probably be wrong. According to fangraphs, Andrus had 98 more balls hit in his zone than Gregorious. That changes the equation, and it's something no casual fans knows about or even cares to know about. We make defensive judgments based on near blindness.
UZR/150 might be flawed, subjective and more, but it's not blind. It looks at every play, and to me, that's what makes it a better evaluator than you and me. Andrus made 75% of the plays hit into his zone. Gregorious made 79%. Gregorious made 110 plays out of the zone compared to 105 by Andrus (in 75 more innings).
The 2015 UZR/150 of these top 8 innings SSs?
Andrus 0.0
Bogey 0.9
Desmond -3.7
Ramirez -5.6
E Aybar -8.0
Gregorious 7.9
A Escobar 6.7
M Semien -10.4
The best UZR/150 SSs last year were:
17.7 Hechavarria
17.5 A Simmons
11.9 Crawford
7.9 Gregorious
The best by fldg%
.988 Simmons
.986 Peralta
.985 Tulo
.984 Hechavarria
.984 Bogaerts
To me, the UZR/150 list is more refelective of who the best defensive SSs are.
It's flawed. It's subjective. But, it's not blind.