@mjh_056
Why a Standard S3 but a DSG R?
Reason I ask is I'd agree that of all the models in the range the DSG possibly suits the R engine the best but if you're prepared to compromise the DSG on the S3 then I'd suggest having a go in a manual R.
With a DSG it's just *snick* *snick* *snick* with the changes and you loose that lovely turbo spool you get with a manual where you can feel the torque build that is soooooo satisfying when you see an overtaking opportunity and want to gradually build up for the move before blasting past using all the revs. With a DSG all you get is *snick* and a "Blaaaaaaaaaart!"
On a more serious note, what sort of miles do you do?
I'm probably the worst person to give any feedback for your choices as I don't get a company car allowance so tend to buy with different criteria in mind and I also run an old banger to take the knocks and do the dump trips that I'd just not want to do in my newer car. The way I look upon it is I work rubbish hours in a not particularly well paid job, but I enjoy my job and work with a great bunch of people (in general) so am not looking for a high flying career and being a billy no mates. The way I think of it is if I had a proper hobby it'd cost money and I'd still need a car anyway so I just combine the two and bankrupt myself every few years... 
Of your options I'm not sure what I'd go for. Depending on how itchy my feet were for a new car too.
The option of keeping the GTD and buying a mk6 GTI is a non starter for me. The mk7 GTD is a great car and can do all a mk6 GTI can do. Having owned two mk6 GTIs and spent a lot of miles in a mk6 GTD or three I can honestly say the GTD is the better day to day car in mk6 guise unless you modify the engine. Then I'd still pick the GTD and modify that engine. So basically, bearing in mind what you already have, I'd keep my mk7 GTD and modify that engine giving it a whole new lease of life. Especially with a DSG with good spec like yours - the manual GTD can run out of revs a bit quickly when modified but the DSG can just *snick* into the next gear very quickly in Sport mode on the days you have horns growing out of your head.
Have a good drive or two in both manual and DSG R's. I my short tenure so far I must admit I do get a bit of a wicked grin on my face when I practice the above mentioned turbo spool as I know what lurks beneath my right foot. I can't (or at least won't as I'm running it in) use 300PS very often but I sure know it's there and the car reminds me as it's pretty eager to go chasing after the hare all the time.
However the mk7 GTI is a pretty amazing car in PP spec. The brakes are great and it feels a lot more light footed than the R. With the 6.5" nav it comes with a pretty comprehensive spec too so if you can get one at a good price then it might be worth going with the tech pack if you can't live without your 8"er or just spending a bit on the 19" alloys being as you want DCC anyway. The GTI is pretty cheap to run as it's better than the R on fuel and runs on 95RON.
They're all pretty great cars for what they are and on different days you'd wish you were in a different model.
I am a bit of a DSG convert, never had before and love it for the day to day driving as it makes it effortless but you make good points on that maybe you get the best experience of an R in manual?! so you added another dilemma as if the DSG in some way replicates my GTD day to day experience mostly then is it worth the jump to an R?
Did mean an S3 in auto too by way, just no other added toys.
My mileage was to be 15-18k a year hence the GTD but is down to about 10k at moment due to role change. Nature of beast as roles do change and locations have to get to change to. At 10k would definitely gone GTI.
Can see what say on MK6 and hence down my list of choices it just the example that saw was a beauty to look at.
Keeping GTD is only an option really if the price they offer it to me is really competitive.
Company car is great and I do get a decent package to choose from but redundancies do happen know of some this year at my place so its good to know that could just hand car back and not be sitting on heavy repayments and that is main reason not taken the ££ and bought/leased privately.
Company car is not all freebie by the way you do get the BIK tax and depending on what go for it can be quite sizeable.
As said previously, the 4WD is a draw too as it is really what stops the GTD being the complete car when it scrambles away in the wet
The only thing really certain of this time is must test drive an R in manual and DSG. Think know what get with GTI and be happy to just select that but R has too many unknowns that can only make judgement on by taking out.
Fortunately the lease company can arrange weekend test drives so be sorting that moment can.
Choices still are
R
S3
GTI
GTD
Another GTD
Or buy my present GTD
If pushed me today for decision heart would rule head and it would be an R