I recently sold my 2005 C6 Z51 Corvette. I am 6'3" 190lbs, have owned two Miatas (NA and NC, neither saw track time). It saw two track days in two years and 20k miles of daily driving. You can see all my "mods" in this thread; https://www.trackjunkies.org/topic/5692-marlin-the-2005-corvette/
As a daily driver it was mostly comfortable. Large bumps like rail road crossing would hit fairly hard but that's about it. I got about 20mpg average during my commute, a combination of some city driving and 80+mph toll road driving. It was pretty quiet on the highway and has power for days. At 85mph the RPMs sit at about 2,000 :) The hatch area can fit a surprising amount of stuff. But a full set of tires are a bit much (in Corvette widths anyways, I fit 4 225/40-18's in there once and a set of 17x7.5" rims another time w/out issue).
Mine had a lot of miles so it had it quirks. A starting issue and the lower shifter box needed replacing, coupled with my super steep driveway it wasn't all that fun to take on short trips to the store. Also, it was a bit difficult to "have fun" out on the street. The car is so fast that you quickly approach unsafe levels of speed. I also had a 1SB (3LT for 06+) so it was loaded out with heated seats and the HUD, which is super great to have. It is customizable for speed, RPM, G force, oil temp, water temp, etc...
On the track the car was a blast. It was fast as hell, cornered great, balance was fantastic, feedback was great. I just really can't say enough good things about it. I had a pretty mild set-up. Power Stop Sport pads, Conti Extreme Contact Sport tires in OEM sizing, ATE Typ 200 brake fluid, and OEM everything else. But for my level it was great. I'm sure a more experienced driver would find the limits of some of those items much more quickly than I.
As you may know, a Z51 package is the one to get for a "base" C6. It has oil cooling, transmission cooling, power steering cooling, larger diameter brake rotors, stiffer springs/shocks/sways, and a close ratio gear box. This is all great for a novice/intermediate type driver on street tires. Once you get super sticky and fast you will want to look at upgrading the radiator (with built in oil cooler) and brakes (a real upgrade, not shitty C6Z brake calipers, they are trash).
For track work the seats leave much to be desired. Comfortable for street duty, but coupled with little bolstering and slick as grease leather, I did lots of bracing with my knees. I had OEM belts with "Cinch Mode" engaged and a CG Lock. I was strapped in as tight as can be.
If possible get an 06-07. The 2005 is fine but has some unique qualities. It requires you to shift into reverse when you turn off the car, it has a "weak" differential housing, and a one year only ECU/BCM combination.
I have not driven a C5Z but I can tell you some differences mechanically.
Stock for Stock a C5Z is just a hair quicker on track than a C6 Z51. Its a bit lighter and has a tire advantage.
The C5 interior and seats are worse than the C6. Most of the C6 interior is pretty ok for daily use, but like i said, track use is another story.
A C5 is a bit easier for track upgrades. You can run a full square tire/wheel set-up on a C5, a C6 you can't without ECU modifications. The C6 uses the TPMS and ABS sensors with a calculated f:r ratio. Mess with it too much and the car can go nuts. Some guys have said there are ways around it, but I haven't seen anything reliable.
You can go to the Spec Corvette website, see what they require (it isn't much, and a very reasonable price) and slap it on a C5Z and you have a very capable car, it will eat up Miatas and shit out fat turd BRZ's all day long.
If you have any questions please feel free to ask. I can help you wade through some of the trash that shows up on the Corvette forum and give you some good options on C6 upgrades.
And to those that like to say, "My 200hp car can hang with 400hp cars on the track, those 400hp cars are overrated!". Just stop. I can post videos of my stock-ass Veloster turbo passing 911's and Corvettes at COTA (not a go-kart track) and I'm slow as dirt. I think most people here know that driver ability counts for a ton, so again, stop. It's embarrassing.