Bit late, sorry about that, but here I am with my story about the quest for a V8.
I really appreciate the comments and insights here, it seems there was little input needed to get this party started.
First of all I need to explain why I came across these two cars, because they shouldn't be compared too harsh as many of u have said. And I agree.
Initially I was looking for an S5, so I went to this dealer to have a look at one, it wasn't there. Some detailwork needed to be done, kinda disappointed, but it happens. So I was wandering through the showroom and "accidentally " ran into the M3 E92. That kinda made me think…..
Here's what my thoughts are on each car
Since I own an A4, let's start with the Audi:
I love the looks, even knowing it's a pimped out A5. It is a class design and I still crack my neck if I see one. The V8 is an awesome engine and the sound is great as well, Quattro provides a safe ride. All together, a great car. But I am afraid the steering-feel will be the same as in my A4 S-line 1.8TFSI /211hp (tuned). I know it's safe as hell (not like the new models) and I totally trust my car, but somehow I do not feel to be in touch with it that much, steering feels disconnected and I guess that's just the way Audi likes to build its cars. From what I understood even the RS5 has the same distant feel. It must be some sort of compromise Audi drivers are willing to take, I am not sure I will ever get used to it. At least I'm curious about …. the darkside

Another small problem I have with Audi are the seats, a.t.m. i have S-line sport-seats, but these do not hold me in place with a little bit of a sporty ride. (Please note I am not a small person, 6.5 ft/14.8 stone). I was hoping the S seats would be better and provided more support, unfortunately, they seem to be even bigger, a test drive might tell me something different maybe. Besides all, I know the S5 is a great, safe and powerful cruiser and I'm looking forward to give it a good try.
The BMW…
So I never even considered buying an M3 until I went to some dealer looking for a S5. Not that I didn't like it before, of course I have seen the video's, the happy faces of everyone who drives it and it is supposed to be the car we all should have driven at least once. I just feel the M3 might be way out of my league at this moment because I have to admit I am not such an experienced driver yet. On the other hand I realize I am the one in control of the pedals and I will take my time to get to know this "bitch on wheels". Maybe I should keep it in 1st gear first few months

. If I buy a M3 of course I will invest in advanced driving courses (did one before), and maybe at a later stage some track experience. Even for a serious test drive I already asked the race-trainer to go with me, he knows all about the M3 and will also give it a go. And I will have it checked by a specialized garage as well.
But, just sitting in the M3 at the dealership makes me wanna drive it, I love how you can adjust the seats for maximum support while still have a luxurious feel. I do like the more upright and active driving position in the BMW, when it comes to ergonomics it all seems perfect. The interior might seem a little dated to some, but it all looks okay to me. To be honest, my eyes are on the road most of the time anyways. General looks, I might still favor the S5, but the M3 has some design details that just scream power and rebellion, it might be a bit overdone but it's all for a good reason from what I have understood. And I love the carbon roof, especially on silver it looks great. What scares me a little about this car is, well, everything, RWD, lots of HP and probably the temptation to wanna "play". The M3 is growing on me, in a good way.
I see both of them as class cars, but in a different league… I haven't driven a BMW so I can't fault it, I have yet to experience it.
Extended test drive's, also on wet roads (we dutchies have the same climate as you do in the UK), will make me help make up my mind. I need to check what running costs will be on both models, besides that insurance and tax are about the same. To drive or be driven seems to be the question and it is something I'm looking forward to experience.
I hope I have been able to explain myself, thanks again for your input, of course I will let you know what the follow up on this will be.