Ring Questions

Hello there. If you opt for a classic-style setting
(solitaire) it's a simple enough job for the average
jeweller to resize (though it's generally easier to size
down rather than up, as Heavyheart says). A competent
jeweller can resize both gold and platinum (plat requires
much higher temperatures to melt and some not-so-adept
jewellers might not want to approach it because they
lack the equipment and skill) as long as the change isn't
too drastic (about 3 sizes). If you have plenty of
jewellers in your area there shouldn't be any problems.

On a looks/wear basis, gold has a higher lustre (shine)
than platinum alloys generally. Both look pretty equal
initially because plat is usually covered in a high-gloss
rhodium finish (the same as that covering white gold).
Platinum will eventually gather a 'greyish' look (patina)
as this wears off. The plus side is that although it looks
scratched, plat doesn't tend to lose weight and can
be polished back to shiny health, while gold tends to
lose weight gradually as it is buffed down. Re-rhodium
plating plat is optional but with white gold it is needed
according to wear and your wife's particular chemistry.

Better wear is one of the reasons plat is much more expensive
than gold (also it's denser and rarer). For sheer everyday
wearability (lightness) and less hassle on repair etc, I'd stick
to gold -- but for something more likely to be passed on as
an heirloom and the like, I'd go for platinum (if I could
withstand the expense ). Good luck.