I asked almost the same question almost a year ago and got the same advice you're getting from every single person I asked. I gave that advice the appropriate weight, which was a lot, but eventiually decided on a drysuit without a tunnel. I don't regret the choice a bit and will buy the same type if I ever need to replace it. The reason is simple: I'm willing to pay any price to be able to install and remove my sprayskirt easily.
My torso is so short that the tunnel on my sprayskirt reaches almost to my armpits the way I usually wear it. Scrunching a neoprene waistband up high enough to get the sprayskirt on and fitting flat stretches my shoulders to the very limit of their range of motion. I actually got a very sore shoulder that lasted several weeks after putting on my shorty drytop one time and ended up ripping the inner tunnel out so I wouldn't have to deal with it any more. Now I put on my skirt and then put the drytop over the top of it like an improved splashtop. I traded dryness for ease of use and I couldn't be happier with it! With my tunnel-less drysuit, I just step into my skirt, pull the front up to my chest, and rotate it back and forth a few times to flatten it out. I never have to reach behind my back to smooth anything out. I couldn't be happier with it either!
The best part, though, is that whenever we get to a good wave where my friends want to play, I can pull up on a sandbar, jump out of my skirt, pop my head and arms out, and be doing sudoku puzzles in less than half a minute. An hour later when I see them dumping the water that got in their boats anyway in spite of their tunnelled drysuits, a just re-dress myself, slide my skirt back on, climb in my boat, and I'm in the water before them. It's very handy!
There's also a philosophical reason for my choice which is so full of obvious contradictions that you don't need to point them out to me. Kayaking is a water sport. You are supposed to get wet. When I went paddling with my drysuit on for the first time, I was almost disappointed. I felt like I was cheating! I got over it, but I do appreciate the streak of cold that runs down my back when I hit a big wave train. I also appreciate having to dump my boat periodically. If my boat stayed completely dry, it would almost seem to me that a crucial part of the kayaking experience was missing. But it's nice staying dry.
I'm just offering the contrarian viewpoint here, but there's no question that putting on a sprayskirt is easier when you don't have a tunnel on the drysuit to mess with. There is also no question that you will get much more water in your boat. If absolute ease of use is the one feature you simply cannot live without, as it is to me, then you might think about a tunnel-less suit. Otherwise I can't think of any particular advantages to it. I think the difference in bulk would be so slight you probably wouldn't notice it at all. As far as rolling goes, do like I do and inflate your drysuit with methane. The extra buoyancy will virtually guarantee a good setup and a successful roll. You'll be amazed!
Happy shopping!
~Dave
"...a light falling sound, as of grains of sand being sprinkled from a window overhead, gradually spreading, intensifying, acquiring a regular rhythm, becoming fluid, sonorous, musical, immeasurable, universal: it was the rain." --Marcel Proust