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If the other fellow has an AA with a low card whatsoever you'll be an underdog, to all other hands you are a favourite.
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This is simply not true. You will be a dog to almost any hand that has decent straight potential and 2 low cards. Look how you fair against this piece of cheese:
http://twodimes.net/h/?z=1391167
pokenum -mc 500000 -o8 ah qh kh ac - 7s 8c td 9h
Omaha Hi/Low 8-or-better: 500000 sampled boards
cards scoop HIwin HIlos HItie LOwin LOlos LOtie EV
Ac Ah Kh Qh 180123 314566 185434 0 0 0 0 0.495
7s 8c Td 9h 185434 185434 314566 0 181067 0 0 0.505
Tiny dog to 789T rainbow. AA with two high cards is not very strong at all.