It does not matter much if you are using DOT 4 or DOT 5.1.
What matters more is what type of DOT 4 it is.
The standard boiling temperature of DOT 4 is:
DOT 4 base
dry: 205
wet: 155
And a few of the racing ones are below.
As you can see its more about which brand / type you chose. I alway like the Castrol SRF, but its bloody expensive, at 45 pounds a bottle. Though it lasts a year or more on the track with no problem, (so pay once rather than two three times)
ATE Super blue
dry: 280
wet: 202
Brembo LCF 600+
dry: 316
wet: 203
Motul RBF 600
dry: 311
wet: 216
Endless RF-650
dry: 328
wet: 218
Castrol SRF
dry: 310
wet: 270
CL Racing Brake fluid
dry: 325
wet: 195
Ferodo Superformula
dry: 330
wet:
AP racing Radi-Cal R4
dry: 340
wet: 204
AP racing Radi-Cal R3
dry: 325
wet:
AP racing Radi-Cal R2
dry: 312
wet:
AP Racing AP600
wet: 320
dry: 199
Performance Friction RH665
dry: 325