1) Oak in red wine, which I like very much
2) Malolactic fermentation in white wine, which I dislike
Putting wine in new oak costs money, so it tends to be more expensive wines that have the flavor profile I like. One thing I love about Spanish wine is that if it has 'crianza' or 'reserva' on the label, there's a legal minimum amount of time spent in oak. And they're relatively cheap (especially in Spain!)
Of white wines, it's generally only expensive chardonnays that get malolactic fermentation (which gives it the "buttery" taste, yuck), so it's a win-win for me. There's no reason to spend a lot for white wine.