In reply to joesmith: It really depends what grades you will be climbing and how much mountaineering you plan to do. You don't say much about your expectations or current rock climbing experience which makes things harder.
As regards boots, the main variations between models is weight and leather vs synthetic vs plastic construction. Plastic boot aren't ideal for Summer alpine so you can probably discount them straight away. That means you are generally looking at synthetic boots (lighter, less durable) vs leather boots (heavier, more durable). If you using boots for less than 30 days/year long-term durability probably isn't as much of an issue, but if you are using then 80+ days/year it may be far more important.
In terms of B2 vs B3, you then just need to balance how much walking, scrambling and easier alpine and winter mountaineering (grades I-III) you will be doing versus how much technical climbing (grade IV+) and steep ice climbing (WI3+) you will be doing. If it is almost exclusively the former, get B2s. If there is more than 3-4 days per year of the later, probably get B3s. It is probably worth erring on the side of B3s, provided you find ones that fit really well!
The C2/C3 crampons distinction are now essentially meaningless. It is better to consider crampons broadly falling into three categories:
- Mountaineering Crampons (12points, dual horizontal front points e.g. Grivel G12)
- All-round crampons (modular with dual or mono vertical front points and 10 downwards points with anti-balling plates e.g. Grivel G14, Petzl Lynx)
- Technical crampons (lightweight, highly specialsed and without full anti-balling plates e.g. Grivel G20/22, Petzl Dart/Dartwin)
You should ignore the technical crampons, you do not want to be walking around the Alps in them. That means you need to decide between Grivel G12s or G14s (or other brands equivalents). If you do not expect to LEAD grade V Scottish routes this year (or next) then get G12s or similar as they are perfect for the Alps and grade III/IV climbing. If you fully expect to be LEADING grade V on a regular basis or plan to go ice-climbing in Norway/Canada etc., then probably get G14s (or Petzl Lynx etc.).
I have just used Grivel crampons for illustration, in all cases the best crampon is the one that fits your boots. The best boots are the ones that fit your feet. So, buy your boots first, wear them until you are completely happy they fit and then take them with you to the shop when you buy crampons.