I see enclosures on sale that say max 500gb etc is this just a selling ploy? How can a enclosure have capacities. On some enclosures it says nothing about capacities
I don't think it is a "ploy" - as that suggests something devious. I don't see where an enclosure should have any limits - if the OS recognizes the drive, it should treat it just like an internal drive. So I suspect the products you are looking at say 500 because that is the largest the company had at the time to test with. I recommend you research specific models you are considering by entering the model number and the word "review" into Google and see what others say. Also, send a note the maker and ask them.
is there any difference with enclosures if buying a external hard drive or buying just the enclosure separate. Looking and touching some of the external hard drives and enclosures it seems a 40 dollar enclosure is built better then a 100 dollar external hard drive that comes with its own enclosure?
I have both. I like the little WD passports. Not too slow and the form factor is very nice. I also bought some Lian Li enclosures a couple years ago. They are SATA or ATA, which I wanted. The nice part about just getting the enclosure is that you can get a better drive than what normally comes in them. Some I have seen are the budget models. I prefer the higher end ones, that are rated for longer use especially in raid setups. But, then again I have some Samsung drives that have been rock solid and were pretty cheap at the time, so who can say really when it comes to a harddrive. Go for the one that offers the connectivity options you want, and don't worry about if it has a drive in it or not. A combo esata, ata, sata, usb2/3 and nic would be nice, but I don't suppose they will make one of those. Sul.
Not really a valid question as it is too general and the answer depends on the manufacturer and model of the products. That said and perhaps something to consider is that an empty enclosure is designed to be opened to allow the installation of a drive. The case of an external drive is not designed to have the internal HD swapped in and out. But those distinctions provide no indication of quality.