I would check out both the Universal and SeaWorld Web Sites. Universal has 3 on-sites hotels, all comparable to Disney deluxes, but closer in price to Disney moderates. May depend on time of year and whether you can get a super saver rate. Staying on-site at Universal has the advantages of having express passes for all rides in the two parks (except for one ride) and also it is self-contained (do not need to take buses to the parks or CityWalk -can walk or take water taxis from the hotels). Hotels do provide shuttle service to SeaWorld, but the shuttles would work more like going from a off-site hotel to WDW - you would be better off having a car. There are no on-site hotels at Seaworld, but Seaworld runs packages through most Marriott hotels in the Orlando area - including some that are very close to SeaWorld - Renaissance, Residence Inn and two new hotels which are opening in July which are close to Aquatica (not sure yet if these new hotels will be under the SeaWorld package deals). You could also stay off-site at either the Universal Area, the Convention Center Area or Lake Buena Vista area which is a few miles south of SeaWorld. If you stay off-site, I think a car would be a must.
If you do both Universal and SeaWorld on the same trip, the packages for either would not include park tickets for the other. You would have to buy those tickets separately.
There is a lot to check into. I would also monitor both this Board and Universal board for a while before you make any decision. I would think the cost of the trip should be less than a comparable WDW trip at a moderate, but you will have to factor in the cost of a possible rental car, meals which you would be paying separately as there is not a dining plan comparable to WDW at either Universal or SeaWorld and purchasing tickets for the parks you would not be staying at.
