Which is the best PDA having all features like bluetooth, wifi, large RAM etc.?

The question you're asking is kinda like what is the best car out there.

You'll get a million different answers! And I don't think that's what you're looking for.

So this is what I have to say:

If you're in need of something like a small laptop, then I would recommend a Pocket PC. It's pretty powerful, has a lot of programs out there for it, and can be a bit complex especially if you're trying to set it up, or back it up. Dell Axim X51v is a good choice

If you need something like a Personal Digital Assistant (PDA) when I'd suggest a Palm, Palm TX is a good choice right now.

A PDA, you would generally use as a helper, assistant. It's really easy to use, in that a couple of clicks to access the address book, or datebook. It's great to keep track of all the things you have to do. There are tens of thousands of programs out there just to make your life easier with such a device.

With both platforms you can create and edit microsoft office files, PDF files, look at pictures, listen to music, watch movies, surf the net.

It simply comes down to what for you actually need the device. Both device, the TX, and the X51v has a lot of memory (that you can expand with SD cards), wifi, and bluetooth.

If you want something thats simpler, yet powerful enough to let you do some work, or watch movies or what not, then get a Palm, if you need something a bit more powerful, and complex, get a Pocket PC.