I purchased am SS 1LE a few months ago. I also had a bolt on C5 before. I think the C5 was a little more comfortable getting in and out and it seemed like I had more room and way more visibility.
I really like the 1LE. Havent made it to a track event or autocross yet. Going to head to the drag strip in the next few week then try an autox with it.
On the street I think the Camaro is the better car. Im kind of a bigger guy and the egress with the recaros isnt the easiest, and visibility is poor, Its hard to see stop lights and the rear sight lines to the corners is almost non existent, but those are about the only gripes I have of the car. Being a newer car compared to the c5 the stuff like AC, headlights, technology, and newer mag ride make it a nicer place to be. The stock NPP exhaust also sounds great and is surprisingly quiet in stealth mode. The car rides and drives well, and handles better than my c5 did with c6 z06 shocks, sways and c5 z06 sized tires. That may be because Goodyear SC3s are considerably more grippy than the RE760s I ran on the vette. You get the stronger trans with the 6th gen compared to the C5z06.
I think the LS6 will probably be more reliable on track compared to the LT1. Not saying the LT1 is bad, but they have known valvetrain problems, not super common but it does happen. Good news is if you follow the GM maintenance schedule they will warranty it for track work. The LS6 is generally considered the most reliable LS type engine for track work in stock form. Kind of a wash with the warranty and the LT1s are pretty reliable, and with the c5 z06 may be more reliable you're on your own for repairs that may be covered with a 6th gen.
I also prefer the LT1 in stock tune over the LS1s and LS6s. The LS1 and LS6 always felt lazy to me with a stock tune. I dont know if its torque management or just the stock tune, they are completely different animals with bolt ons and a good tune though. The LT1 seems to be more versatile and have more power everywhere on the stock tune. Mat it at 1500 rpm the LT1 seems much more responsive and willing to give you everything compared to the LS1/6s ive driven. The LT1 also makes power everywhere, it will happily accelerate from 1500 rpm in 6th, makes good midrange and pulls hard all the way to 6500.
If money wasnt considered Id take the 6th gen every day over a C5. Count the cost and it becomes a harder decision, the C5 is a hell of a car in any trim for the money.
As far as modifying a SS over a stock 1le, I considered this because my wife wasnt a fan of the recaro seats. I ended up going 1LE. I like the e diff which isnt available on the normal SS. The 1LE also gets a better shifter which is much nicer, and doesnt seem like a big deal but changing a shifter on a 6th gen is apparently a big deal. IIRC the 1le gets stiffer bushings which is a common upgrade for the SSs but also a pretty big deal to have done. The 1LE gets extra coolers. The 1le gets different springs, sways, wheels, brakes, and the no lift shift is optimized for track work compares the the normal SS which is more drag race oriented. I was willing to get a 2SS with mage ride, NPP and a manual but I never found one, and now Im pretty glad I didnt. The 1LE seems to be the more complete package for track work and the track warranty is definitely worth something. I also think the 1LEs will probably hold their value a little better which is a nice thought, they arent exactly rare but they are harder to find than a normal SS, and I think they are actually a little special. If you are going 18 or newer you could do a 2SS 1le and get most of the luxury stuff you get on a normal SS. FYI if you get any 1LE with recaros it has the equipment for the heated and ventilated seats even if its not a 2SS. there are aftermarket setups to get the ventilated seats to work, Im hoping someone comes out with an OE style integration to make them work but nothing yet.
Side note: The wife really misses my C5 and wanted a C7 or C8. I considered a C6 z06 which would have been less, than I paid, and they have been my favorite vette since they came out, but I wasnt keen on spending more than 30K on a car to just immediately pull the heads and have them sent off for repair, and Im way too anxious to just let it roll. Ive also done some clutches, torque tubes, and diffs on c5s and 6s. I never want to do one again. The 6th gen and 1le seem to have less drivetrain failures, and I will be drag racing this regularly I as have all my cars, so that played a role in my decision. I have watched my friend literally eject a diff out of a stock C6 on street tires at the track. I really like the idea of a conventional clutch swap on a car Im going to beat on.