What makes a good Battleground ?

Meaningful choice.
I could end that entry here, but let me explain ;)

In PUG Warsong you can
1) get the flag and move the flag
2) defend the flagroom
3) defend a captured flag
4) get a captured flag back
5) kill players on the field
6) organise

In PUG Arathi Basin you can
1) try to capture any of the flags
2) defend any of your flags
3) figure out where to move next
4) kill enemies
5) organise

In PUG Eye of the Storm you can
1) Do all the things you can do in Arathi (5)
2) capture a flag
3) recapture a flag
4) wait with the flag somewhere until the center is free
5) defend a flagcarrier

In PUG Strand of the Ancients you can
1a) drive a tank or
1b) destroy a tank
2a) plant bombs or
2b) defuse bombs
3a) defend a graveyard or
3b) capture a graveyard
4) kill any enemy on sight
5) figure out where to move next
6) organise

In PUG AV you can (if no faction rushes)
1) defend towers
2) blockade points of interest
3) defend graveyards
4) attack towers
5) break through points of interest
6) attack graveyards
7) scout
8) (re)capture a mine
9) stealth (w/wo the skill) into the enemy base
10) kill enemies
11) collect stuff to summon stuff
12) zerg
13) oranise

In PUG AV when any party rushes you can
1) wait for 1 minute in a cave then klill a PvE mob after riding on your mount for another 1 minute and waiting for another 5 minutes

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I'll stop here.
Let's now look at rated BGs:
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In rated Warsong you can
1) stay together and protect your flag carrier while trying to overpower the enemy group that does the same. This is the best strategy, trust me.

In rated Arathi Basin you can
1) do all the things you can do in PUG Arathi (5)
2) talk about it while you do it

In rated Eye of the Storm you can
1) Do all the things you can do in PUG EotS (9)
2) talk about it while you do it

In rated Strand of the Ancients you can
1a) drive a tank or
1b) destroy a tank
2a) plant bombs or
2b) defuse bombs
3a) defend a graveyard or
3b) capture a graveyard
4) figure out where to move next
5) talk about it while you do it

In rated AV you can ..
Rated AV is too epic for WoW. No rated AV.


Fazit:
Warsong will be boring. The rest can be interesting. From a pure tactics point of view Eye of the Storm will be the most fun. Considering the environment, Arathi will remain the best BG. EotS looks ugly and is highly unimmersive.

AV would rule them all.