The flight is better for a colossal margin.
"When you cast a spell of bloody rage or sorcerer that causes damage," it is already a very special case: you should not do it very often. Sorcerer's spells are much more effective in controlling the battlefield, damage or improvement than in direct damage. Hurry Usually, it will offer much more damage than any explosion, for example. You might want a explosive spell among your known spells, but probably not more than one, and you will generally have better things to do with your spell actions and spaces.
On top of that, reducing resistance to spells and energy is not as valuable. It is much better to use more reliable spells that are SR: No and do not inflict energy damage at all. For that matter, whenever possible, favor spells that have no salvation; a touch tactile attack is easy and some spells don't even need it. There is nothing a typical creature can do about it. solid fog, for example. Also, even if you want to do damage to energy, spell resistance and energy resistance are not as common. All that adds to this class characteristic that is not used much time.
On the contrary, flight is one of the most important skills of the game. If you have it while your enemies don't, you have literally-infinite options like them. It can move to positions that simply cannot. You can dictate a lot about the battle. And, on the other hand, if the enemies have flight, you need it a lot, because otherwise you are the one with infinite fewer options. Each character needs to find some way to get on the air by medium levels. Even in dungeons with low ceilings, the flight still protects it from traps, the most difficult or dangerous terrain, pressure plates, etc.
Honestly, my biggest concern with the wings of heaven is to wait until the ninth, you should get fly to 6th level, and then change it to the tenth. You will want to use the flight as much as you can. You will feel limited by the limitations of use of Wings of Heaven, wish you had more. At some point, some permanent form of flight could reach the wings of the sky, and that will be a shame, but the perforation of blood will not be something that I miss much even at that time.
The only reason to consider blood perforation in this situation is if you are consciously avoiding the flight, as part of a gentlemen's agreement between the players and the GM that the PCs will not fly and the GM will design the matches accordingly. Such a campaign has much merit, because the flight is messy, complicated and incredibly powerful in ways of warping the game.