We have tried to put together a simple guide to comparing pencils leads from different brands. It is actually very hard to achieve this and represent it well on screen, but this is a fair representation of the various brands we have available. Since most non-specialist brands lean towards an HB lead (the middle compromise between an H hard lead and a B black lead), there is little to distinguish between the pencils.
The Blackwing pencils demonstrate the highest degree of change which is not surprising - their pencils don't follow the standard H and B grading you find, but they are still graded from the harder 602 pencil to the softer Classic with the Pearl in between.
This chart was done on Rhodia paper but you will also find very different results if used on different papers, especially a paper with a grain to it. Since pencils will be used for drawing quite often, it follows that you may find the paper plays a big part in the result.
Top marks do go to the Blackwing pencils, unsurprinsingly, but other pencils that deserve a mention here are the Faber Castell 2001 Grip, and the Viking pencils. Both are quite smooth and consistent in how they write.