Core Drill through Clay hanging (roof) tiles

Hi,

Have some hanging reclaimed clay tiles (on timber frame/ply/battens) to drill through for a 40mm waste. BC have said it's fine. Should I use a diamond coated core drill that is normally used for internal bathroom tiles like this:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=180573290004&ssPageName=STRK:MEWAX:IT

or a chunkier diamond (TCT?) style core drill normally used for masonry like this:

http://cgi.ebay.co.uk/48mm-x-150mm-...DIY_Materials_Plumbing_MJ&hash=item5adc56664d

Obviously would prefer something less likely to break the tiles as replacing a broken tile half way up a wall is not easy (for someone like me!), so wondering if the internal gentler bit may be better, albeit slower.

And yes, I will switch off hammer action!

Many thanks.

use a diamond core

Sorry Kev, you mean the heavy duty sort with arbour/guide drill and four or five longer teeth normally used for masonry, right? , not the shiny thin things with a ring of diamond glitter round the top more normally used for bathroom tiles (which I've also seen advertised as diamond core bits, just to confuse things).

Thanks.