I love 911s and I would say yes it is worth it. Monetarily maybe not but the experience is, in the nicest way the 911 is a step up in all respects from the G29, especially where you sit. Luxurious, fast and comfortable it sits in that niche spot and is more of a GT than sports car just like the G29.
The convertible isnt the best variant, unlike the Z that was designed to be a roadster the 911 wasnt and you can feel it. Its a completely different model and old but I had a 996 4s convertible and it was heavy and you could feel it but the experience was great and I tended to drive it like a GT whereas the Z4M I have is much more raw and connected. Im sure the newer ones are much better from that perspective but it is worth baring in mind you can't defy the laws of physics and the 996 4s was about 18-1900kg for an old car it was a lot to lug around and it obviously had the 4wd system too which isnt the best experience either the RWD cars are more purist but I love the wide body look and in the winter it literally got everywhere.
This was new years day and me and my dad went for a drive up Hartside which isnt far from my family home and had a blast... the Z4m was all over the place the 996 was planted and inspiring... niche conditions and im sure lots probably are itching because there is snow... I like to drive them all year round.
I have experience with the 996 4S, 997.1 CS coupe, 991.1 CS coupe, 987.1 BoxS and the 981 box GTS. I love them they are a step up in every measure but they are pretty ubiquitous and not as rare but it's because they are so good.
The 997 was my favourite it is basically a better Z4M in every way fabulous drivers car. The newer models have a twin personality, the 991 is bigger, heavier and a very comfy GT but put it in sport or sport plus and it's an absolute animal. The 996 and 987 were the only ones I owned but my dad has had them for like 20 years now and we do a lot of driving and swap half way. Ive been lucky to have the access so it's been less of a need for me.
Porsche 911's, Yorkshire Porsche Festival, Lotherton Hall, Leeds by
Tom Scott, on Flickr
We've been all over Europe in them and had a complete blast
Z&P Eurotrip UK to Monaco 2017 by
Tom Scott, on Flickr
Go have a go in one and see what you think. Only you will know once your in one.
Money questions are personal and the reason I have a Z4M is because buying the 911 I want I need 50-60k plus the Z4M and in my current situation with a baby and 2 dogs I can't justify it, nor is it practical but because the M isnt worth a lot I can justify having it as there isnt anything that competes at the same value.
If I wasnt in my current situation I would have one in the garage right now.
That being said at 70k there are a lot of options, ive always fancies a 355 or 360 which is in this category or really push it and you could get into a 430. Those are another level again but are much more sensitive to milage and cost to look after. If Ferraris aren't your cup of tea there is loads of good options that are worth exploring.