The institute is part of a much bigger "home study" institution, offering all sorts of subjects. If you are worrying if the company will be around, it probably will. I have not taken the photography course, but know people who took their interior designs and landscape architecture course and were very happy. That was my mother, and she is now working partime in both.
The course offered cost around S$1400++. Just bought a D70 kit from fellow CS not long ago. Want to spend money wisely. If the course is not worth to pursue, then I might as well invest my money into accessories, and just take more photography.
Not saying the course is not good ah...but remember, it's a 'home-study' course which means you have to read course materials, understand, go and apply, then feed-back results to 'lecturer' to comment and make suggestions. This works very well for some people.
If you're an organised and focused sort of person, you could consider gathering and structuring your own research materials, project assignments, research in bookshops/internet, absorb, apply and post up in various forums for both technical as well as artistic critique. Cost? Electricity, time and perhaps printing/ink costs if you print out articles.
Of course, in the old days, NYIP would send you physical materials like negatives and such for you to practise your darkroom work, printing etc. I suppose now they would be e-mailing or sending CDs, especially for digital darkroom work.
Whether cost is worth it to you all depends on the quality of their course materials, any programmes/applications/digital goodies etc. Another consideration could be whether you're comfortable discussing things with Ang Mors via electronic means. I notice that some Asians, who are very talented, have major problems learning from American or European forums and discussions because Ang Mor speak/write the more powderful England and there may possibly be some cultural differences that could invariably influence the discussions, or at least the language they use in terms of examples, analogies and artistic influences.
I'm sure others who have gone through correspondence courses are in a better position to comment and advise.
Check the inet or phone directory for all the photographic societies listed in SG and check with them. I believe SAFRA also offers courses, as well as some private businesses that sometimes list in the Workshops section of CS.
On a personal note. These courses are ok if you are attempting it on a self improvement route. If you want to go commercial, suggest you take up related courses in NAFA/Laselle or other overseas establishment
Generally you learn more in a course where you see the teacher face to face and interact with fellow classmates. Assuming that the teacher in NAFA is as good as those in NYIP and both are about the same cost, it makes more sense to go for the part-time diploma.
If you are asking which is more recognized, then i would venture a guess that the NYIP is more renown.
But whether these teachers or qualifications can make you successful as a worldwide commercial photographer is a different question.