Honestly I'm not crazy about either split, but if I had to choose my preference would be "B", BUT you don't have any hamstring time in "B". Don't forget hamstrings!
If size is your goal, we need to realize a few things:
Your nutrition is what will put the size on, assuming your training hard and heavy. So, if you're not counting calories and macros, your training split doesn't matter. Figure out your TDEE, add a 10% surplus every day and start there, using the mirror and scale as your guide. If the scale goes up and conditioning still looks good, keep going. If the scale goes up and conditioning is getting puffier, pull back and slow down. Adding LBM is a slow and steady process, despite what most people think and do. If you haven't been training too long you should be able to put on size fairly quickly with a good, consistent, well executed plan. If you've been training longer it'll be a slower process. Either way you have to be extremely meticulous if you don't want to get fat.
Regarding your question of hitting muscle groups once or twice a week, there's no "this is better than that" answer. Both are good and must be done correctly when implemented. If you're hitting once a week, then you kill the muscle, lift heavy, incorporate some intensity techniques like drop sets or forced reps, extended sets etc., and recover until you hit that muscle next week.
If you hit twice, then you lower the volume a little bit and lose the drop set stuff so you can recover by the time you hit again 3 days later. For example, right now I recently started a 2-a-day program, training twice a day and hitting everything twice a week. So you can bet I cut the volume down and am not doing crazy drop sets. I'll cycle this plan for a few weeks, then take a "de-load" week for recovery and growth, then repeat the cycle.
So again, it's not that one is better than the other. Once per week body part splits are the gold standard for a reason, they work. But twice a week is also very common and works well when implemented correctly. If you're trying to bring up a weak area, higher frequency is certainly a way to do it. So, if you want to hit something twice a week, go for it and see what happens. But, be aware you shouldn't be doing the same workout twice a week that you would do if you were training them once a week.
~Abs and calves should be trained twice a week regardless of your split~
- The WAY you train will also play a significant role in your growth, not just the split. Getting some heavy compound movements in and keeping everything in the 8-12 rep range to increase strength and add size is the way to go, keeping in mind you must use a weight that targets your desired muscle and doesn't have you swinging your body around to get your movements in.
Use the heaviest weight you can to keep the tension and initiate with your desired muscle, try not to get the upper body movement and knee movement that most people have when training with free weights.
If you want to grow you MUST have a great MMC (mind-muscle connection) and feel the targeted muscle doing the work. This takes a lot of time and extreme focus throughout every rep of every set of every session.
Make sure you're getting a ton of sleep, otherwise the best training and nutrition in the world won't mean a thing.
So, just to recap, pick a split that makes sense, train hard and eat to grow. It really takes quite a lot of consistency. Try not to get caught up in the "I want to add "x" pounds of mass". That's impossible to say. Execute a well designed plan and see what happens, think LONG term, like at least 6 months to a year if you want to look noticeably bigger.
And of course, be sure to post any questions along the way!