I confess that being a sad engineering type I've got a bit of a collection of assorted slide rules - including several flight computers of various types.
The one I like best, and lives in my flight bag for everyday use, is my CRP-1. I have used both versions of the E6B - in use they're virtually the same as the CRP-1; but I'd not recommend the metal E6b for the simple reason that it bends too easily out of shape if sat on - the card one is scruffier, but much more durable (and probably the cheapest thing on the market).
The CRP-5 is basically a posher CRP-1, and I'd be very happy to own one.
Basically they're all the same - but in general if you want a Rolls-Royce FC, get a CRP-5, on the other hand if you are on a tight budget buy the £15 laminated carboard E6b (or Pooley's equivalent, the CRP-4). But any of these will be quite good enough for learning and any normal PPL (and most CTPL) flying. For that matter, a WW2 era RAF "Dalton Computer" will do most of what you want, it just might not use knots or litres.
G
N.B. I use my FC for virtually any flight of more than an hour's duration.
N.B.B. I don't suppose anybody has a set of instructions for a Jeppessen CR5 or similar have they - I have one in my collection but there's a few of the cleverer functions on it I haven't worked out for myself.