For a modest OC the Newer MB utilities seems to do a pretty good job.
For a Higher OC you are better off going manual.
Used the MB utility for an i5-750 to get nice 3.2 GHz and the Asrock utility (i5-2500k) was good upto 4.6 (Backed of to 4.2 as not much difference between 4.2 and 4.6). They both are overly aggressive on Vcore. What i did is verified stability (using prime95), then started backing off on vcore to just above the point of instability.
NOTE: when running prime95 MONITOR your temps (ie for both the i5-750 and i5-2500k If using a stock HSF will raise temps above comfort levels) Also Prime95 is good for verifing your +12 V rail under load.