Matt,
The M is appropriate for your size. You might like to read my boat review posted at
https://www.riversports.com/blog/ . If you intend to carry a bunch of extra gear weight you could consider the L. Otherwise, the M is going to feel more agile and super enjoyable.
Matt,
Here's my thinking. First, know that each size of the Karma boats drive as if they are smaller. Their performance is awesome. Secondly, unlike many other designs, Jackson creek boats tend to accommodate the top end of their recommended paddler weight range without a significant reduction in performance and they rate them based on paddlers weight alone (knowing that additional gear weight is to be expected) . Thirdly, you're 20# below the top end of the range for the Karma M. That said, you can easily enjoy either the M or the L size.
Regarding the Karma, the stability at each size is off the chart. For me the M was practically unflippable (It rolls up easy peasy. I just never got flipped by a rapid). The M lends itself especially well to a bit heavier or a taller person that will leverage it easily. I think the L will be necessitate that even more. Being 2" wider, the L will be for you like the M was for me. It will be unbelievably stable, but very roomy inside. Which sounds desirable, but it may feel like a lot of boat if you were to ever be getting chundered in a major hydraulic or needing to nail a super tight must make move in fast, powerful, high consequence, creeking.
Frankly, I think the L is most appropriate for persons over the 210# range. If you chose the L you may desire to do a major custom outfitting similar to what I had to do for myself in the M (see photos) in order to feel more secure and dominant in it.
On the other hand, if you chose the M size you may want to do what I did in the S. I took the 3/4" thick seat pad out and replaced it with 1/8" foam, and I reduced the thickness of the knee padding from about 1/2" to about 1/8". This allowed me to lower my center of gravity and gain about an inch of vertical room inside for a roomier, more comfortable and powerful leg angle. Now my S is quick edge to edge, fast, secure, comfortable, and super stable for me.
The M is rated for a up to a 220# paddler. Compared to the L, the M will be more agile in performance and still be super stable. Not as stable as the L, of course, but not as massive feeling either. However, if you intend to load the stern with lots of gear, then the L will prove superior for you.
Like others have stated, it is a personal preference. People your size are loving the L. However, in my opinion, you can chose to be over the top stable and maybe less agile in the L (although it will drive like it's smaller than 9' long and 28" wide). Or you can choose the agility, Formula 1 race car performance, of the M and likely find it's 8.5' length and 26" width is still battleship stable and yet makes you boat more dominantly. I've often cautioned people about getting too big of a boat. I like the idea of "me driving the boat instead of it driving me". One thing is for sure, though, the Karma's performance is supreme in either size for you. Let us know what you decide.
PS: If this doesn't help you and others contemplating which size is best, I encourage you to contact Tony M at 4CRS for an opinion from he who crushes the Gore Race and the Bakers Box.