The 10yo is a great drink. Very zesty, but going through sweetness to grapefruity and finishing with custard. As with all Bruichladdichs, it's non-chillfiltered and no caramel added.
The 17yo, as I remember it, is very similar but more butterscotchy, and the flavours (especially the citrus fruit) become softer, rounder.
I don’t particularly rate the 20yo Flirtation. It’s a good malt, but not an outstanding malt, and certainly not worth £70 a bottle to me (although The Whisky Shop in Edinburgh stocked 20cl bottles of the 1st edition, which was a great way to try it without splashing out too much). It’s drier than the 10yo, but I don’t think the fruity flavours marry so well with the dryness.
Infinity 1st edition is fabulous. Sherried, toffeeish, creamy, still that fruit flitting around, cocoa, and the finish goes on and on and on. The best Bruichladdich that I’ve tried, unless I want peat and then it’s onto the next:
3D second edition – Moine Mhor. Another truly fabulous whisky. Different from the three above as it’s peated (and more so than the original 3D). You can still taste that characteristic Bruichladdich fruitiness through the sweet peat. It’s very robust, with chocolatey sweetness and custard, and beautifully complex.
Haven't tried Rocks yet, but it's always on offer in supermarkets, so I'm sure I'll get round to it
When I was at the distillery, Mark Reynier compared the 10, 15 & 17 to wines, with 10yo being the aperitif and 17 the digestif. Maybe try the 10 15 or 17 (buy a miniature or maybe a bar near you stocks it) to see if you like the base first, then I’d go for the Infinity or the Moine Mhor as they’re definitely so much more interesting.