i would suggest not going for voidghost atp cuz i am pretty sure it will get a substantial nerf very soon. but i would say outlaw is a pretty good one for long term

Have you checked out any content creators' videos where they do mech ranking? Those would give you the most comprehensive info and a good sense of the meta. 

Beyond that list, perhaps mechs that have received buffs/nerfs recently (and are still good) are good options to pick first, since them getting nerfed soon is less likely. As morax said, outlaw is one such example. Redox and mimicker are others. Surge and deathwalker are still decent options despite their nerfs. 

Finally, if you have the choice, I would say invest in good weapons (if you haven't already) before you invest in good mechs.

silly me but what exactly do you mean with PvP? i sort of know hangar showdown, 1v1, CPC (control points), deathmatch or ffa but pvp.. isnt it just player versus player.. wth would that mean? you would have different choices of mechs for different modes really..

 for example Aegis is great for control points even though its not legendary.. you can spawn with shield and defeat multiple enemies to protect control point.. similar may go about Zephyr (but i dont use it anymore) since i struggle to choose perfect hangar full of legendaries.. super fast mechs are great for control points (nomad, surge, lacewing not bad), my best control point grabber is nomad, its a beast.. i can end up with 5-6 points captured per game, even more.. the seeker will help ro get rid of some pain in the balls player with artilery weapons or something (wont help against roofers, unless you give it long range something and attack the furthest). the deathwalker is also a good grabber.. its fast when ability active and it still captures control point for at least a second after it dies.. i used to love shadow with charge rockets or the eclipse with pod guns.. 

the deathmatch.. seeker is always cool.. deathwalker too.. i have salvor (healer) one of my favorites.. if it has couple suppressors and does long range.. citadel is not bad.. but deathmatch is tricky, it depends on map what weapons and mechs work best.. i would say compound beams for citadel.  

ffa is close combat.. citadels, dreadnoughts etc..

hangar showdown..

deathwalker, parasite, eclipse..

i used to like outlawbut its super slow.. maybe with charge rockets idk

its really your preference.. i could push a lot from a lot of mechs if i didnt have choice.. for example vortex is super slow but give it charge rockets and its flying between control points while active ability makes him a hard to defeat grabber.. orion is still a choice for many 17k hangars.. hard to oppose that opinion it has very important ability for a sniper of sorts..  there are although average mechs that are more or less nothing special.. like brickhouse or onyx, they are usable but nothing special. 

volti could be your choice for 1v1. if you like to annoy enemies