Have you driven either of them. If not, do so to find out which one you prefer.

I looked at the Golf 6 when it was introduced. The interior to me was way below the expected VW quality and the overall design did not impress me. Very surpised since I had owned 3 Golfs in the past and been very happy. Walked away.

Move on about 6 years. Golf 7 just out, had a look, definitely an improvement. But then I looked at the Mk 3 Leon. Very impressed with both the design, spec, trim and especially the drive (140 PS SE TSi), bought one a few days later. 2 years on I am still more than happy, nothing fallen off, no faults at all.

Best bit was the saving I made. A Golf with similar trim and engine would have cost me £5000 more to buy.

I say Leon every time but drive both and make your own mind up. Compared to the Golf 6 the Leon 3 is light years ahead.

IF you have a desire to purchaase one of the VW varients the Golf/Lean/Skoda are all based of the same parts and basically it down to which one you like best.

They are indeed based on the same parts but the Golf Mk 6 the OP is considering is from the previous generation wheras the Leon Mk 3 is based on the brand new VAG MQB platform which is very different. The Golf Mk 7 is based on the new MQB platform but will be way more expensive than a Mk 6 Golf.

Personally a 3 yr old Focus 1.6 Zetec is on pair and notable cheaper than a golf also having good reliabilty.

We also looked at and drove the Focus when we bought the Seat but IMHO the Seat is a much better car. The 1.4 TSi engine is an absolute cracker giving tremendous performance and almost diesel economy. Over 13000 mile ours has averaged 45 mpg.

I am no impress with Kia/Hyundai as second hand options

Not sure what the above actually means but we also have a Kia Ceed which is a very good car but it falls a long way behind the Seat for comfort and refinement. The 1.6 petrol engine is very poor needing a lot of revs to get decent performance and as a result the economy in the real world suffers.