Need Help Please : Images Organization, Renaming OR Tagging , What's b

Do you rename ur pics or just tag ?

I was organizing my pics ,
n i've like 700,000 pics & wallpapers . some are sorted , some not .

i was thinking on some kind of organisation format .


Now question is, if i organize by developing some kind format , what's better ?

Renaming OR Tagging ?

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IN RENAMING :

Advantage:
if i rename my pics , by some format ,
all pics will be alphabetically sorted
thus FASTER ACCESS when i open a folder.

Disadvantage:
there can be chances of duplicates formation, later,
if i download the same picture from internet again,
n store it with a slightly different name.

like eg: Alaska ~ Original filename
Alaska - Denali Park ~ Original filename
Denali ~ Original filename


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NOW TAGGING :

Advantage:
if i keep the Original filename intact,
there will me LESS or NO chances of duplicates formation,
since Windows can replace images with same filenames, while moving them.

Disadvantage:
For Sorting of images by Tags, For a large collection,
Sorting Time CPU takes can go a bit quiet long .


As my collection keeps growing, it's 700,000 already,
and if they get 1 million, or more.
it may take 15 min or 1/2 hour
for large number of images to get sorted by tags .

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i've a Quad core CPU though, 4 GB DDR3 RAM.

So , Which approach should i follow.
RENAMING or TAGGING ?

Need Advice !