It's not. Well, at least, not technically in the Danger Zone. However, if you are looking at odds in one of the random rooms, decreasing the opponents attack or power increases your probability of winning by much more than increasing your own attack. This is especially true at low numbers. For instance, let us compare two characters that are evenly matched at 5 power and 4 pills. If you lower your opponent by 2 power, it's now 20 vs. 12, which is a 62.5% chance to win. Now, if you gain 2 power, it's now 28 vs. 20, which is only a 58.3% chance to win. It's weird, but in a purely mathematical sense, that is what happens.
The other aspect is psychological. A character with 9 power seems like a challenge but can be overcome. Watching your own character go from 6 power to 4 makes the play feel like a waste of pills. Or at least that's what I feel like, but I'm no expert.
IMO they are both the same, and if you meet an Ulu Watu or Banger player vs an All Star deck, just cancel both bonuses and see who's got the upper hand. To me these are the Best bonuses in the game, none other; since it is a game of math, and when it comes down, it's the multiples that count the most, clans such as these can bait you with 1-2 pills so its mainly strategy and a calculator,
The minus power bonus is really only better in a way over plus power in dark corners where there is randomness, but then again nothing is really fixedly better in rooms with randomness because like the name implies, it's random, even a card with atk 1 can win a card that is pilled. I dun really consider games in rooms with randomness as a place to be calculative about tactics, but for those who need to know, it's pretty much normal math in randomness areas.
Lowering one party's power as opposed to increasing another's power also lowers the common denominator, thus increasing the percentage chance most of the time for the guy with the higher atk. Take a plus 10atk or minus 10 atk on 2 cards with 20 atk each: 30/50 = 60%, whereas 20/30 = 66%, mainly because the denominator is increased, making the higher atk "larger" percentage wise.
Im not exacting that minus power definitely increase the chance over plus power, but a large majority of the time it should.
Ewww actually i encounter some good problems when i was facing some good decks-ulu watu-pussycats
3 pillz-feelyn(-2 power) vs tanaereva-2 pillz
so its 15 vs 16....tanaereva will still own
3 pillz gabrielle(+2 power as bonus) vs tanareva-2 pillz
so its 21 vs 20....tanaereva will loose against gabrielle
TAKE NOTE gabrielle is a version of feelyn...all are with its bonuses