I cannot decide which one is better to use on my planets???

If you have Quasi Chaotic researched, i would go with attack, then you can add the 50% buff with the lazuli darmines, giving 10 more % than the nexus.

It really depends on the max stats of your structures.

If you have +1200 att structures and the +750 defense ones then it would be better to use the +1200's. It also depends on what passive bonuses the planet has and what artifact structures you have.

Overall though you want the highest possible invasion defense you can muster. Oh and dont forget about population, its no use putting 10k inv def on a planet if they can kill the population in a few hits. Its all about costing as much time and effort as possible to make you planet not worth the resources to take it.

Edit:
But then mitch you can get -30% att but only -15% def.

Also, nexus is 20%+20% = 44% and darkmines are 25%+25%=56.25%

True, and also Def helps reduce dmg done to the pop. It is really all about personal preferance.

Usually researched population structures aren't worth the space, just use attack or defense to increase invasion defense so they can't invade.

well, IMO I think pop and defense is the best way to go with a little attack to irritate the attacker
because with a large pop and high defense, gonna be a pain to go through.

I researched obviation barriers just for the planetary defence. I haven't lost a single planet thanks to them. Pop one or two on and most enemies will not even bother. I also find population structures very helpful. Having 600 population with over 2K defence is a pain to get through.

2K def is not a pain to get through.

With 2k def and 600 pop it'll take me 30 clicks to get rid of them..

shut up... It works for me...

Preventation-wise, defence and population are the way to go. A little attack never hurts.
Invasion-wise, depends on your structures. REMEMBER: defence can be cut by 15%, attack by 30. For every 1200 defence, you need 1326 attack to have the same, debuffed, invasion defence..

seriously though man if you only have 2k def and I wanted your planet it would be gone

My comparison was between 1 top level defence and attack. You'd need around 3 space worth of attack (eg 1200 minefield and a phase cutter) to get the same invasion defence as 2 space of defences.

$5 says i have a 90% invasion chance on every single one of your planets. How about you send over your planets locations via Wi-Fi and i'll take a crack and your well defended planets.
On another note i find it's good to have a mix of defense and attack. I usually have about 10k defense and 5k attack after buffs.

wow, @$$hole alert.
Guys, for me this is the balance. Enough defence to stop most, MOST (not all) potential attackers. Simply bricking all my friggin planets is stupid. Whatever works for you, works for you. Whatever works for me, works for me. I don't ridicule your tactics so don't ridicule mine. I offered a potential answer to a question and everyone over double my rank attacks it like they have a damn right. Screw you.

thanks for the help guys I think i'll stick with defense and pop, but only when I have used my planet artys and structures, so about 2500 def, on most structure's, i nicked a really good planet off some rank 6** and I have about 6k def, for a rank 69 it's the best I could get without being stupid and over the top.

I'm telling you like it is. 2k defense is NOTHING. Even a lowbie legion full of rank 200s could take that if they organized some back ups.

And if they do then hell ya I'm gonna brick the planet. If they take it I'll take it back or I'll sell it. But what I'm saying is that throwing 10K defence on every planet is a waste of space and credits and you won't get the most out of your planet production.

Firstly, you won't be able to brick the planet IF THEY TAKE IT. secondly, 10k defense takes up about 6 space. not a huge loss. Ths is the last time i post because i can't be bothered arguing with your stupidity and ignorance.

3600 defence takes 6 space... 10K is over double that. Ya, its a big loss. You are also about double my rank and in a much stronger legion with better resources.
I'm done defending the strategy that has yet to fail me.