Well I'll give it a shot. I'll just give an overview, otherwise I could go on forever. If you want a really good guide, check out this link writtend by Hydroguy:
www.disboards.com/showthread.php?t=1162599
DDP- dining is not as good here because you don't get a set amount of food, you get a set amount of money per day to spend on food. You also can't use the vouchers in Downtown Disney restaurants and there aren't that many amazing restaurants in the parks or hotels. You also don't get change when using the vouchers (which could prevent you from saving money), so for example if you buy something that is $4.95 with a $5 voucher, then you would lose 5 cents in change, but if you are all out of $5 vouchers, then you need to pay for it with cash (which destroys the point of a dining plan) or with a $10 voucher which would lose you $5.05 (which can add up fast).
Tickets: The main difference in tickets is that everything 2 days or more is a park hopper (except for certain non-mainstream tickets), so no need to purchase an add-on. Mousesavers always has the best places for ticket discounts, just like for WDW tickets.
Photopass- Same system I believe. They give you the card and you can buy the pictures at home.
Time of year to go- I personally like going during the busy seasons and getting to the parks early because of the long hours and all rides and entertainment running. However, if you like going during low crowded times, you will only have long hours and full entertainment (fireworks/fantasmic) on the weekends. Plus some rides might be down for refurb. Summer weekdays are usually manageable if you can do the heat. I see you have gone to WDW in May and June. Great times to visit DLR too.
Transportation- Unlike WDW there are no buses or boats. There is a monorail, but it's not a recommended source of transportation. Driving is not a problem, unless you stay very far offsite which is not recommended. So the main transportation is your own two feet. Everything is within walking distance, including tons of cheap offsite hotels. It takes about 2 minutes to park hop or reach DTD, which is quite different from WDW.
Where to stay- Offsite is the recommendation on these boards, but I can see that if you are coming from the Boardwalk and Saratoga Springs, you might find some of the offsite hotels "not a full experience". Most of us don't stay onsite (or justify staying onsite) because there aren't as many benefits by staying onsite and there are some offsite hotels that are actually closer to the parks.
EMH- No EMH here, but Magic Mornings are early entry into DL (not DCA) 1 hour early on Saturday, Sunday, Tuesday, and Thursday. Onsite guests can use MMs every day offered during their stay. All tickets 3 days or more come with 1 MM. Check out my MM thread:
http://disboards.com/showthread.php?t=1675403
Hope that helps a bit!