I don't think a foot in length is a serious concern. Far more important is the layout that works for you and the STYLE of the interior that you like. Subtle differences in the layouts can be very significant once you begin camping
I am not a full-timer but I have become addicted to studying the layouts of these silver beasts the past few years AND I bought mine to travel solo most often. The above quote is good advice but you may lack the experience in a camper to know what you need. I will tell you as the owner of a 25' twin with a "traditional lounge layout" that I have more than enough storage for my stuff. A twin is handy in floor space and has three outside storage areas plus under bed storage AND lockers too. Aside from that, what I would like more of is kitchen counter space and a more comfortable sitting area that can seat three comfortably (for when I have others). The comfort seating though is still important, even for one. I cannot imagine that longer trailers are easier to back other than one vs. two axle considerations but that too is my lack of knowledge or experience. Perhaps three axles does something I do not know in the backing process.
So, between the models you are talking about I believe there is a closet difference and a lounge difference. I will tell you that as a single person I prefer the 28' layout. The sink spraying the couch is a non issue since there is one person. What I note is that if I choose to use the side dinette for kitchen counter prep, I can leave the mess and walk over to the lounge and eat AND sit in a normal straight-on direction and watch TV or something and clean up later. I like that L Lounge. The models that have the seating with dinette in the front and lounge on the side are not as beneficial to a single person use (my opinion) although nearly all floorplans now in AS are this way. The real reason for this is more sleeping area. How many beds does a single need?