R4s are cool because they're less obvious than 2CVs, and so a bit more anarchic. Everyone has got a 2CV, or knows someone who had one once, but R4s are for the connosieur (I used to know someone who thought that my R4 was a 2CV...)! And they've got those funny little handles attached to the front wings, which are the last word in automotive chic! They're a really cool shape with nice detailing too, and the hidden interior door handles are always a laugh when the uninitiated can't work out how to get out. That the steering wheel is in a sensible position (unlike the 2CV's, which feels like a bus steering wheel) is an added bonus. They're better for carrying stuff (2CVs are surprisingly small inside, and the only usefully-sized opening is the roof - not much help if you want to carry something heavy as well as bulky), and you don't have to grease the R4's kingpins every 1500 miles. Tyres are cheap too (unlike 2CV tyres, which are a funny size unique to the Citroen and thus bloody expensive).
2CVs are cool because they make a nicer noise, are easier to work on, and you can get parts for them (you could build a brand new 2CV from parts straight off the shelf). The 2CV engine is also one of the best designs in the history of the universe; expensive to make, but a true thoroughbred, and utterly indestructible - almost a grand prix engine in miniature. A 2CV is also faster than an 845cc R4, and much less tiring on a long journey, and they were designed to run on unleaded fuel (useful these days).
I used to commute fairly regularly between Ringwood (Hampshire) and Coventry, which is 150 miles each way, almost exclusively on motorways and dual-carriageways. My 2CV and R4 (an 1108cc GTL) both used to manage it easily, although the R4 would do the journey in marginally less time. I once drove nearly 7000 miles from Hampshire to Lisbon and back in the 2CV (via Montpellier, Andorra, Barcelona, Valencia, Costa del Sol, Gibraltar, Sevilla, the Algarve, etc.). That sort of journey in some cars would make you never want to see one again for the rest of your life, but I'd happily do it again in the 2CV. I've not tried it in an R4 yet...
The ultimate would be a hybrid combining the best features of each car, but failing that, one of each (which is what I've got).
