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As someone who likes Magmar a lot more than Magmortar, I can't really say I like OP's pic more than Magmortar. It's certainly a sleeker and 'cooler' design, but otherwise its lacking in personality and an identity separate than Magmar.
I don't love Magmortar's bloated design, but it serves a practical purpose as increased surface area and an expanded body would be necessary for a Pokemon with such an extreme internal temperature. I don't really like the cannon arms on either Pokemon, I always thought they were unnecessary.