Well there is a great read and thread in this very forum. Its currently on page 2 of this " VS " subforum. It was started by @
WolfpackS2k . His insight is very good, and a lot of the thread that follows has tidbits of great insight.
That being said, as my journey continues through the world of cars/modding/racing my wants evolve. As does my point of view or reference. Lastly, your question is very vague so I will do my best to interpret what i think you are trying to find out. If you give me more specific concerns then i can share more focused opinions or observations.
First things first, lets not turn this into a 987 vs 981 vs 718. I have driven all 3, and tracked two of them on a very short course (1.2 Mile). They are all Porsches, so the fit and finish is above the BRZ and S2000. The Cayman(s) and the BRZ feel very similar when driving them on the road. The S2000 doesnt feel like either one in my opinion. But there is a weird kinship between the 987 and the BRZ/FRS. Maybe its the size, the cockpit, the guages....I honestly dont know, but the BRZ feels like it was influenced by the P-cars. Except for one glaring difference, the engine placement.
I could ramble on for days about these cars, so I am going to try and be brief and therefore not all encompassing.
The BRZ is a great beginners car for tracking. It is a great beginners car for modding and learning some wrench turning. It is less fun on the road than a Porsche, but much more friendly than the S2000. But it is not a GT car like the Porsche is, what i mean by that is the S2000 and the BRZ are pretty bare bones. The P-car is still more insulated and muted than either the 86 or s2k.
The Porsche is the best blend of daily driver and racecar. In fact no one does it better than Porsche in my opinion. Yet, somehow i still feel the Porsche is too soft, hence why i prefer the S2000 to a Porsche. In addition, I like to be able to do virtually all work on my vehicles. With a P-car it is not really do-able.
S2000, a great affordable car (compared to Porsche) that has fantastic driving dynamics. A great powertrain. A much larger learning window, as you progress as a driver. You can DIY the hell out the car, unlike a Porsche. It takes to mods very well. But, it sucks as a DD for most of the population. Both the Cayman and the BRZ are much more DD road friendly.
So if you want:
A do it all car on a budget, and you like to turn wrenches - BRZ
A do it all car and have the funds, and dont mind not performing your own mod/maintenance - PCar
A track/weekend car only that gives up the practical side of the BRZ, but is sharper on the track then - S2000
I dont need the practicality of the BRZ, but i want to do all my own work. The fact that the S2000 is more affordable to me(than a Porsche) is just a bonus. If i didnt want to perform all my own work, I would be in either a Cayman R (987) or a 981. The 718 is fantastic. The handling has little improvements all over the place, over the 981. Not big ones, but the steering isnt quite as dead feeling. The power difference is unquestionable. The 718 base is as fast as my old 981 S.
But I wont pay for new one. I also like to track my cars, and until i see how the turbo'd 2.5L engine handles heat while on the track I will just sit back and watch. But i imagine in 5 years or so my stable will have a 718.
I hope that sheds some light, but if it was no help at all, please let me know what info you are looking for and I will do my best to share.