I have the Miele 30" all fridge and all freezer, and love them. I essentially approached the problem backwards. I do freeze a lot, and have had an upright freezer in my kitchen or pantry for the better part of 20 years. I would be fine with a freezer on bottom, 36" fridge if I had an attached garage or other easy access place for the freezer. In this house the kitchen was the best place for the freezer, so a prettier full sized upright freezer was part of my remodel plans from the beginning. And having that, I didn't need a freezer in the fridge. I've seen two 36" over/under units installed side-by-side, mostly before the column units became popular. This is good if you want/need more fresh food storage than frozen, but there's more that can go wrong. Either your fridge-freezer units have one compressor so they share air and sometimes compromise between the two compartments to maintain temperatures, or you have dual compressors with the fresh and frozen compartments on separate systems, and essentially four units instead of two. An all fridge and all freezer are just larger, simpler units. As to looks, 6' of uninterrupted refrigeration can be a bit...blank. You can use styling to make this better. Some people have cabinetry panels made so that they look like a bank of smaller doors and drawers. Some people put art on the doors. Some use large, decorative pulls. I have 5' wide, tall units, which gives more of a vertical appearance to the refrigeration, with big, honkin' custom pulls that break up the space. Some all fridges (a certain model of SubZero, for sure) have a window, which breaks up the surface and gives you deeper shelves (no door storage. Another option is to put the fridge and freezer in different locations. Many people find that they don't need both at the same time/place. The freezer might be closer to the pantry storage and the fridge closer to the prep zone, for instance. Other people have done very clever designs that make the pair with a surround so they look like an armoire, or other kind of contrasting idea. And some just leave them as they are, figuring that appliances should just be and look like what they are. You haven't mentioned your price and performance preferences. I believe Frigidaire makes freestanding all fridge and all freezer for a very reasonable price. Thermador makes mid-range built-in columns (i.e., integrated all fridge and all freezers in several sizes). The top end are built-ins by SubZero, who make a lot of different sizes and shapes, and Miele, whose columns are the same size and shape as Thermador (same factory), but whose electronics and features are by Miele. Which ones you choose depend on your budget, style and preferences for interior arrangements and features. If you go to a website like AJMadison you should be able to get a good overview of what's available.

While I don't have recommendations for all fridge/all freezer units, I wanted to suggest another possibility. In our kitchen remodel we put in a full-size Samsung FD, and an apartment-sized (24" wide, counter-depth) LG. The LG holds about 10 cu. ft., pretty evenly divided between fresh foods and frozen foods. I call it my "kid fridge" and use it to hold milk, juices, other beverages, yogurt, fruit, and cheeses, as well as ice cream and frozen baked goods. The kids know exactly where to find their drinks and snacks, and I like having the beverages at eye-level. This solution has worked out very well for our family of 7 (plus one dog and one cat)-- we have plenty of space for both fresh and frozen foods.

I don't have any experience with the freezer drawers, but I do have the Perlick fridge drawers. I needed a 24" unit and they seemed to be the best in that category. SZ would probably be my choice if I had needed 27". I saw the CR article that appeared after I'd bought mine and noticed they didn't rate Perlick. They didn't even seem to know abut them because another of their criticisms was that none were energy star rated, but the Perlick are. They have a high BTU variable speed compressor that runs quietly and efficiently. It does have an off switch on the front. The 2 liter bottles will not fit standing. We thought they would, but it isn't a big deal for us. We generally have milk, juice (about 2 gallons of each) and large pitchers of iced tea and filtered water in the top drawer (along with jam for PB&J sandwiches or toast) and water bottles and other beverages in the bottom one. The drawers did cost as much as many full size freestanding fridges, but they turned out breakfast room hutch into a marvel of convenience and eliminated a lot of traffic across our kitchen during meal prep and eating times.

So this goes to function and dividing things. First, I think it sounds like a nice idea as long as its symmetrical. Asymmetry makes me crazy. I moved my fridge with top freezer to the other side of the (pocket) door into the mudroom. It's next to my full-sized freezer. So much counter space now! Within 2 months, it crapped out on me. I picked up a Frigidaire dorm type fridge and stuck it under the counter. Within a MONTH, the fridge started working again, but the full-sized freezer crapped out. Luckily, I was due a binge-cook 'n freeze, so I was low on frozen life. I crammed everything left back into the fridge freezer. Now I'm considering trying to make the bottom part of the fridge the freezer ( can they be set that low? ) and the top the fridge ( can that be set that high? ) Since I can't fit much other than beer cans (dorm fridge, remember?) I'm thinking I might try to set the whole thing down to freezing for ice cubes and small frozen soup, 'getti, or other single-serve frozen stuff I live on. Anyway, I'd dump the full-sized freezer, although it's only 5 years old. If I knew then what I know now, I'd have purchased tall and thin, vs. short and wide. Takes up SOOO too much space! So I guess yes, I'd split them. I must ask, though, in a U kitchen, if space is that tight, why are you blocking it with an island?