what are the pros and cons of each ? I have always shot 4 inch vanes but the small blazers have got me thinking

From what I was told: (Someone correct me if Im wrong.) The short vanes and fast but less stable, so they are better for short shots. The longer vanes are more stable, which is more accurate for longer shots, but tend to fly slower.

I have shot both and prefer the short vanes... dont know why, they just seem to shoot better for me.

I agree. I have a lower draw weight (44#) so I go for the shorter vanes. I have switched to fletching my own vanes and adding the 6 deg helical has made an amazing difference.

With carbon arrows and a couple of 2" vanes.

Besides, it's a lot cheaper than a new $900 plus bow. And I won't need any primers.
I hope the added speed won't ruin my homemade target. I'm rather cheap you know.

I run blazers on everything, haven't ever had any issue stabilizing arrows out to 80yrds. I'm not 100% convinced 4"duravanes stabilize any better than 2" blazers. Feathers are a different story, but duravanes, not so much. 323fps out of a 73lb Bowtech Destroyer 350 with 395grn Goldtip XT hunters, 425grn XT hunters out of 70lb mathew monster at 280fps, 50yrds is boring, 80 is a ball.

someone told you wrong, the "Blazers" are by far more stable than a longer vane.

I've shot 4" vanes & feathers for years. Same set up, went to blazers last year & see no difference & I practice my Broadheads (3 blade 125 gr fixed) through 60 yds..

Unless you are counting inside/out X's, you won't know the difference.

Just a matter of information, but Blazers are vanes.

But it's also very common vernacular that guys designate "vanes" as duravane type non-engineered, non-textured vanes, hence the differentiation. Blazer-vanes are a very different animal in terms of induced drag compared to a smooth body plasticized "vane" (duravane).