Both Conkledurr and Heracross are fine, they are both very good physical attackers but Conkledurr has low defensive stats unless you use Bulk Up as a power up for 2 or 1 times,while heracross is good with a little base Sp.def but mega evolveing it would make it slower but un mega evolved it has okay speed. Conkledurr is onley wek to flying, psychic and fairy while herracross and its mega form are weak to psychic, fairy, fire and is very weak around flying type moves, Anyway the two Pokemon are both great. If you have a guts ability herracross it will be very offensive if it has a status condition or holding either flme or toxic orb, swarm ability is good for powering up bug type moves like pin missle and mega horn, its hidden ability Moxie will raise its attack whenever it defeats a opponent and mega herracross ha skill link so bullet seed, pin missle and some other keep doing attacks will be perefect. Conkledurr with its hiddden ability, Iron fist raises the power of fist moves such sky uper cut nd thunder punch (to bad close combat couldn't be one of them) guts is its first ability which is good with status problem or flame/ toxic orb to make attcks and sheer force I forgot. you chose ok
for easier info: Herracross and Meg Herracross: http://bulbapedia.bulbagarden.net/wiki/Heracross_(Pokémon) and for Conkeldurr http://bulbapedia.bulbagarden.net/wiki/Conkeldurr. I hope I helped