what do people think is best and any problems with them . buying new bike and have the choice at no extra cost
Having just finished a climbing camp I have a few things to say on this subject, though I am talking about performance orientated riding with reasonably strong to very strong riders.
Firstly a chainring change is a lot more disruptive than a sprocket change on rear cassette. With that in mind on though on a triple you often don't need to double shift making each change quicker you change chainrings you change chainrings more often, this makes is harder work & a real issue when on steeply undulating roads (stronger riders with triples were getting dropped by weaker riders on compacts when at racing pace). With compacts you almost always have to double shift when you change chainrings, with STIs this means you lose a little more momentum on a chainring shift where you'd need to double shift on a triple but this impact was far lower than the more frequent chainring changes required by a triple rider.
Riders with a climbers physic (generate less power but have a higher PWR) were better off with a compact & a closer cassette setup where as those who where naturally sprinters (more power but lower PWR) faired better on doubles with a wider ratio cassette. The only times the people on triples to a real advantage was those running a wider ratio rear cassette on the really steep sections (>20%), then really they rode on a 39/52 double all the time except when it got really steep & they could drop to the bottom chainring. This is very similar to what SRAM have done with their road ratio 12-32 cassette compared to their MTB ratio 11-32 :
12, 13, 14, 15, 16, 17, 19, 21, 24, 32
11, 12, 13, 15, 17, 19, 22, 25, 28, 32
The 11-32 is a much more progressive cassette however in the context of road riding that jump from 24t to 32t is almost exactly the same as dropping to the 30t chainring with ##-25t cassette, exactly what the guys using the triples were doing but giving a much more efficient gear change!
For the record using the same cassette a 30t chainring gives you 1 more lower gear than a 34t compact & 2 more than a 36t compact.