First of all, all Blu-ray (or DVD) players are not created equal. That’s why you can buy DVD players as cheap as $25 and Blu-ray projectors from $70 to many hundreds of dollars.
Seriously though, in this day and age, you just don't want to be feeding any home projector a DVD when there's Blu-ray out there. A good Blu-ray player will also make your old DVD's look better than your old DVD player.
Sony is a major manufacturer and the inventor of Blu-Ray. Sony is introducing 4K Blu-ray players
Of course Blu-ray is a whole major league step above DVD in terms of resolution (about 5x as high resolution in terms of the number of pixels) Picture quality of Blu-ray is also dramatically better. You can get a really good Blu-ray player from under $100 with $250 dollars. Almost all but the least expensive Blu-ray players are able to update themselves using your wireless network Blu-ray itself is an evolving standard, with 3D added a few years ago, and 4K is the new thing. Note that the most popular Blu-ray player out there is Sony's legendary PS3 gaming console, now being replaced by the PS4. Almost all Blu-ray and DVD players will offer you a choice of outputting an interlaced signal, or a progressive scan signal. Progressive scan is a better image, but more on that later. Let's just say that if you have a projector you want a Blu-ray player. 1920x1080 resolution sure beats the whatever, out of 853x480. That's a big difference on a 40 inch LCDTV on a 110" projector the difference in resolution is nothing short of massive.
So let's stick to Blu-ray players. Years ago for highest quality everyone used Component video outputs, but HDMI has become the standard since about 2007.
Component video is essentially analog with the potential problems and artifacts that analog brings. Much better is all digital HDMI although the source material may itself (a movie ), may have started out as analog (film).
Quicktip: A digital cable – be it HDMI or DVI - will perform flawlessly, or will be obviously be very bad. Long distances are problematic for HDMI but these days there are many solutions if you need to run HDMI 30 or even 80 feet. (In the old days about 20 feet was the maximum.) Some HDMI cables claim high throughput and long distances, but don't deliver. I've bought cables claiming they could do 3D at 30 feet, that can't even do a clean 2D at that distance.
HDMI carries audio, but other than lower cost home entertainment projectors such as Epson's Home Cinema 2030 or Viewsonic's PJD7820HD, don't expect more expensive home projectors to have speakers. Thus, image goes over HDMI to your projector while sound gets to you sound system either by using an AV Receiver that handles your switching, or by feeding the digital audio directly to your sound system from your HDMI sources like Blu-ray players and satellite boxes.
Expect to start seeing a number of new Blu-ray players start offering upscaling to, and the ability to output the original source as upscaled 4K. And a number true 4K Blu-ray players will be available in 2014. Audio from your Blu-ray player comes in basic stereo outputs plus coaxial and optical. For surround sound you do need coaxial or optical. Optical is the better way to go, so look for it on the Blu-ray player you select, if you have a need to separate audio for video. That's so typical for projector users - HDMI delivers the image to the projector, while some other solution needs to deliver the audio to your AV receiver or other sound system. (With a Plasma or LCDTV they have audio built in, so unless you are by-passing those internal speakers, you can just deliver the audio over the HDMI cable.)
With all these choices – what works best?
- Interlaced or Progressive output
- Digital (HDMI / DVI) or Component video
- 1080p output, upscaled 1080p to "4K", or true 4K content?
Interlaced or Progressive Output
If available, you want progressive output - that is: 1080p is better (really higher resolution) than 1080i. Almost all cable and satellite are 1080i maximum but we are starting to see some 1080p coming that way.
Digital or Component video
Unless there's a compelling reason, go digital (HDMI) over Component. But, for example if you wired your house for component video 5-10 years ago, know that you can get essentially the same quality, if done well.
1080p and Higher Resolution - 4K is on the Way
The HDMI 2.0 standard with 4K resolution support as of this writing, isn't quite out yet. Nor are any 4K Blu-Ray discs, but we are getting close, 2014 is the year that 4K starts meaning something. Everything supporting 4K will presume digital as the primary, more ideal solution.
I've reviewed the few 4K projectors out there (both Sony), and, Wow! True 4K on a 100 inch or larger screen is a huge improvement. Really good upscaling gets you only part way there, but far from all the way. Feed it the best signal, and that will be digital. But start saving, you'll want a 4K projector down the road when they are affordable.
What brands to consider?
I don’t evaluate Blu-ray players, but again, the Sony PS3 is pretty much the industry standard, as I expect the PS4 will become. There's a relatively unknown brand called Oppo that makes very high performance Blu-ray players for relatively affordable prices. Many if not most Blu-ray players now offer 3D, which is a good thing, because almost all home theater and home entertainment projectors that have started shipping since 2011 are fully 3D capable (and it's great)!
Personally, besides two PS3's I have a Panasonic, and a Sony Blu-ray player. Still, I use the PS3 for almost everything. BTW my PS3's can output true 4K still images (to a 4K projector) from digital cameras that can do at least 9 megapixels - that includes many very affordable point and shoot cameras. I've done it! When 4K Blu-ray players start hitting the market, they will, like 3D players before, tend to be very expensive. So, if you don't see a 4K projector in your immediate future, prices will be lower when you do buy that 4K projector.