So which one is better? Before I answer, let me just state for the record that of all visual dictionaries, these are the most common and probably the best around. The Oxford provides a lot of information right of the bat with greetings and setting yourself up in an English speaking country from, in this case, an Arabic speaking one. The DK dictionary begins with parts of the body, people, feelings and works up towards other useful vocabulary. It has beautiful pictures, which is something DK is known for.
The winner? DK Arabic English Visual Bilingual Dictionary.
Yes, the choice doesn't require a lot of fluffing each one up or a whimsical, "well, it depends..." No, DK is definitely better. A lot of it may be preference, such as size or cartoon style vs. real photos, but the main reason for me is DK is simply better for an English speaker who is learning Arabic, or whatever your target language is. The Oxford series is clearly geared more towards learners of English. E.g. there is no pronunciation given for the Arabic, so if you can't read Arabic well, you're out of luck. Either way, pick up both, but definitely pick up DK first.
https://www.amazon.com/Oxford-Picture-Dictionary-English-Arabic-Arabic-speaking/dp/0194740102/ref=sr_1_3?ie=UTF8&qid=1501737905&sr=8-3&keywords=oxford+english+arabic
https://www.amazon.com/Arabic-English-Bilingual-Dictionary-DK-Publishing/dp/0756649838/ref=sr_1_2?ie=UTF8&qid=1501737993&sr=8-2&keywords=arabic+english+visual