We just went from a R-25 Classic to a 2017 C-28.
Some thoughts:
It feels huge compared to the R-25. Maybe not so much of a jump from the R-27.
Feels great to be able to go faster when you choose to do so.
Visibility is amazing from the cabin.
The hull is very different and handling in rough water not as stable as the RT.
You need a ladder to get into the bed! Seriously, it is way up there from the floor of the v-berth. We use a step stool. Getting out of bed at 4AM to use the head is a gymnastic challenge.
The door to the head only opens about 45 degrees when it hits the v-berth cushion. We will be modifying by getting a new center aft v-berth cushion with a bigger door swing cutout.
The cave in the C-28 is much larger than the cave in the R-25. We store all kinds of stuff down there. Could still store a binch of stuff and have room for a non-claustrophobic teen to sleep!
For us the coffee bar across from the head is a complete waste of space. Would have much rather had an upper closet with drawers below.
Immediately take out the bolster under the mirror in the v-berth. You get much more sleeping room if you sleep head to stern with the booster moved to storage.
Don’t like the A/C main shore power location on the C-28. You end up needing to run the cord all the way down the port side if you do bow in starboard ties at the dock. Our RT with the connection at the helm was more practical.
The swim platform is literally awash at higher cruising speeds. Big wake.
In rough seas a ton of water goes over the top of the C-28 flooding the cockpit. Don’t leave anything out that you don’t want soaked.
I am still getting use to the much newer, more feature rich and faster Garmin 7612xsv. We also went from Yanmar to VP so lots to learn about the engine monitoring capabilities of the VP D4.
Finally, we looked at the newer R-27 diesels but, for me, having the D4 in the C-28 sealed the choice between the two.
Note: Big difference between 2012-2015 C-28s and newer models. For one thing they waste tank was at the stern in older versions. Waste tank under port side cabin in newer models. Not sure exactly when they switched. 2016?