I was advised from various different roadies and a LBS man:

Sora for budget, will work decent.
105 for best quality, reliability, but price wise not better value for money compared to sora.

I went for 10 cog 105 groupset. Thought it would be better in the long run (Ultegra and DuraAce compatible, 10 cogs seemed more "future proof"). Got it 2nd hand, except for STI brifters. Those should be bought new only.