The two known max techs in wiki:


Lets take an amount of space you might use on a really good planet you really don't want to lose, that has a common denominator for both these building sizes: 14 space for "defenses" is 20-40% of planets space. Such a planet is probably very large or massive, so 25% loss of production. Now, let's say you are ok taking this loss the planet is a 15x mega rich toxic or something else you cannot afford to lose.

Now, comparing both of these, with legion bonus:
7 barriers = 2400 * 7 = 16800 defense
2 cloaks = 1600 * 2 = 3200 cloak

The question really is, "which protects my planet better?" Well, to have any shot at scanning, you need something like X-Manifold Detector and some buffs. Cloak is an absolute barrier for anyone without a certain tech level, and still a good barrier against others. Someone with 6400 scan (high tech, high rank players only) still has a 50% miss chance given the last formula I've seen for this (which might change in the future). I am not sure how many players have 3200 scan, but they need that AND your nice planet has to be randomly selected AND they have to succeed on scan.

For defenses, I have seen something like 7k planet total defenses vs. 7k attack is 40% chance. Even with 17k defenses vs. 5-7k (high rank players), a high level legion will invade it eventually through sheer number of invasions unless you flux (and you have a good chance of losing it before that). This is ALMOST absolute defense against very low ranks with low attack, and if they take it they probably won't know what a flux is to keep you from taking it right back, so the issue is almost moot. Middle ranks with coordination can still present a problem here.

Also, if cloak ever goes to size 2 like defenses, the choice is clear here regardless of costs I think.

So which is better ... which one blocks more players effectively from invasion do you think ?

I vote for defence.. planet cloak is worthless, i carry more scan then your example unbuffed 24/7... 10k+ defence makes me think a few times before i liberate that planet..

someone write it up on the suggestion and ideas forum, i vote for +1 planet cloak are useless

cloaks are useless... ive scanned many planets with anti-tachyon sattelites, i just havent taken em cause i know i cant hold em and they arnt worth fluxing. defense is definitly the way to go. when youre sporting 16000 defense the only people who can take that planet are the very best players in the game.

Cloak USED to be the #&$#, but with new advents in scanners, and the reduction in defenses, it's just something you want a little of to keep the rif-raf away.

At your rank the answer is simple. Although the question is asked a bit wrong, since cloak can't block invasions, only prevent it all together, if you will, in my book cloak is the winner. You can do the repeat-able mission for lesser fluxes and you should have a good supply of flux probes. Probe your planets weekly and flux the ones seen by others. Got more seen planets than able to flux ? Trap the hell out of them until able to flux. You can't really have enough defense on any planet. I for one build both cloak and defense on my planets. All of them. And keep traps on every planet that is seen.

I've got 8 flux orbs and can get however many I need. There are only a few planets that I invested enough buffs into to care about them (in other words, not replaceable by a randomly found planet). I have 10% space allocated to defenses on my planets, high ranks don't really care to steal anything in my experience (the whole quantity over quality thing, and I spread upgrades around equally), and low ranks can't get through the def to invade (but I will shell up and flux orb it anyway after a week, not going to waste a real flux). For me, the space efficiency of defense seems to win out, there's no reasonable way to block someone with high tech scanners (too much space usage for the protection).

The problem that I'm running into is that most of my planets that I've upgraded using toxic purifiers and planet optimizers on are common or uncommon( gas and toxic planets). So basically they are more likely to be scanned. I use to just put defense on them, but a lot of lowbies seem to be finding them. So, now I'm leaving enough defense to be a hinderance and adding cloak.

Need to consider population too..
lots of folks overlook that..
it can help give you more time to react and increase invasion cost considerably.