There is a DIN all about Overseas Staff Colleges, which you should look at.
My recollection is that Indian Staff College is not directly aligned to ACSC and therefore does not carry PSC/PSC(J), but for a definitive answer see the DIN. Also I know that some of the arrangements (in terms of which courses are aligned to what) have changed recently.
But a year in Paris, drinking 1/2 Btl of Claret daily at lunchtime was not entirely unfullfilling in itself.
some of the statements presented as facts may not be entirely factual. Some are definitely false.
Going on overseas Staff Courses does lend a broadening to one's vision. This next part is true (as opposed to the semi-fiction above): My Canadian colleague on French Staff Course with me was Quebecois, a French-speaking Canadian. Competition within the Canadian AF for a place in Paris is high. It's considered the plum course. He felt that he had psychologically returned to the "Alma Mater" by getting a year in Paris with his French relations.
After a year of being mercilessly teased by his French "relations" for his "funny" version of French, a realisation dawned on him. The Canadians are far more firmly placed in "Le camp Anglo-Saxon" than le monde francophone.
By the end of the year, he'd stopped speaking French. I like to think that my whispering campaign, each lunchtime, helped.
Also of interest were the African stagiaires from, predominantly, West Africa. They were always amused by the blatant (and not entirely subtle) propaganda being pushed about how "France is Europe & Europe is France". They were amazed that other Europeans on the course were not too upset bu this. The Germans, of course, couldn't be; else they be accused of anti-French feeling etc.
For my part, I used to simply reply with Confucian-like retorts such as "Does the Lion fear the noise of the Hyena?", or "Don't you have a younger brother in your family who needs to be indulged and guided?".
On one module we were taken to Brest and shown round an old SSBN. The "hidden" message was clear: Look at our power; dont mess with France. The foreign students were suitably impressed, at this example of French technology and strength. The guiding officer was less happy when I pointed out to the group that the majority of the machinery inside the sub all bore makers plates declaring their origin as being factories in the Midlands.
It was a good year. I'd encourage it for anyone. AS @eodmatt pointed out - where else can a subaltern enjoy a year of misbehaving without collecting extras.
When I went through the system (admittedly many moons ago), the only Staff Colleges deemed equivalent to UK ACSC were Germany, Pakistan, USA, Australia, France. Canada. So, for example, if you attended Canadian Staff College you graduated with psc (j) (CAN). I thought India came with a psc pass. There were options to go to other Colleges (Italy, Norway for example) where you qualified with 'osc.'
Clearly not all Overseas Staff Colleges are deemed equal or good enough to be deemed psc(j). However, volunteering for an OSC is not a bad thing. I had the 'must go to UK staff course to get on in the future' earbending and ignored it. I spent a great year elsewhere (psc (j) earning) and it did my career no harm at all. In fact it helped my get two jobs I wanted downstream - one on a Multinational op and one overseas staff posting.
Personally, if I had my time again, I'd go overseas again - Canada, Australia or Pakistan....
They tried to send me to Canada, I bucked and squirmed hard enough that I ended up staying in UK. Why? I hear you ask. Because a) Canada started earlier than UK and it would have meant missing an Op Tour as OC b) I wanted a COS job and was pretty sure I wouldn't get it if I went to Canada.