advise wanted on changing cassette

You can use an Ultegra OR Dura Ace cassette with your 105 shifters & derailleurs ... but, why pay more?

alfeng, thanks for that, i've seen an offer on the ultegra cassette and its only £3 more than the 105 cassette.
how much difference can the ultegra cassette give? i imagine not a lot.

I think the 105 cassette is just slightly heavier than the ultergra cassette. The Dura ace cassette on the other hand is significantly lighter than the two. I am actually debating right now if the 65 grams is worth twice the cost for the Dura ace vs. the Ultegra for my "hill climbing" cassette. I spent the extra $ for the cassette that is on the bike most of the time and went Dura ace.

How about this idea? It seems the smallest cogs on a cassette wear most quickly: we spend more time on them, and they also have fewer teeth to share the load. When my cassette is shot, I can tell because the little cogs start to skip – big ones are fine. Why not get a Dura-Ace, when the time comes, replace just the smallest few cogs at $15 bucks a piece. I’d think the big weight saving are on the large cogs and spider assembly, titanium on Dura-Ace. That my bright idea!