I think blackjack has benefits that poker does not. The main benefit is faster growth of money, and an almost nonexistent ceiling on how much money you can expect to make, since table maximums can be VERY HIGH.
In Poker to my knowledge, most pros measure their winnings in Blinds per hour.
In blackjack winnings are directly proportional to the amount of money wagered on each bet. and can easily be doubled by simply playing two hands at once, or even three if your gutsy..
In poker as you bet higher and higher, it will become more difficult to find players willing to play higher stakes, while simultaneously the players will likely be of higher skill causing you to have a lesser, if any edge over them.
Growth of money in blackjack can be exponential, while poker is exponential to an extent, but eventually becomes more linear as you reach higher betting levels.
Tournament play is another region, both games come in tournament form, and both can be constantly won by skilled players.
I would have to suggest that poker tournaments are more popular and easier to find than blackjack tournaments which are more of a novelty.
You get WAYYY more comps in blackjack than poker, like mad comps, i usually can get 20-50 dollars per hour in comps on my card just by betting a couple hundred per hand, if i were betting thousands, ti would just be rediculous what the casino might throw at me for free.
Lastly, poker is growing in popularity very fast, in the past, peopel seeking to be professional poker players were uncommon, and the "chumps" they feed off of at the tbales were plentiful, Now with more peopel aspiring to be professionals there is likely a higher average skill base, making profit margins lower, and harder to attain. This is juts a theory, im sure its true to some extent but by how large of an extent i cannot say, i know little about poker.
Anywho, poker and blackjack are the two most popular and pratcical games that you can earn money from, there actually are other exploitable games, but they are not worth the effort.
To compare them by dollar
In blackjack you can make about 0.4 - 0.6 times whatever it is that you bet per hand on average, every hour
In poker, to my knowledge it is measured in big blinds per hour which also only to my knowledge is aroudn 1-2 BB per hour.
I vote blackjack since thats my game of choice, since i feel that you can get more money into action per period of time, and per period of time, earn more money. Edges in blackjack can grow enormously when players employ tactics beyond counting cards alone, and can reach figures around 3%+ AVERAGE, some tactics can attain edges at 10-20% when employable, and one tactic can create single betting oportunities with a +53% ev, though only one at a time and generally only couple times during each shoe.
Myself, Professional Blackjack player