I am currently involved in running a Dangerous Journeys campaign and I regularly play D&D 3.5. The two games differ in the following ways:
Making a first level character in D&D is relatively simple and can be done in a short amount of time even when all the material is available.
Making a starting Dangerous Journeys character is hours of work, with many decisions to be made along the way. This leads to characters with a lot of individuality but is a big commitment for first time players. Dangerous Journey characters start a lot more capable than their D&D counterparts.
In D&D you have 6 stats, in Dangerous Journeys you have 18 stats that add together to make an additional 3 stats(Physical, Mental and Spiritual) which then have other scores derived from them.
D&D is a level based system where characters advance by gaining experience points. Upon gaining each level the character advances significantly.
Dangerous Journeys has no level system, characters gain points that they can spend increasing their stats, increasing their K/S (skills) or gaining joss (luck) points. This means that characters tend to advance incrementally, one small change at a time.
D&D 3.5 has a manageable number of skills covering most things that a character might want to do.
Dangerous Journeys has a huge number of K/S areas (Knowledge/Skill) broken into three main groupings Physical, Mental and Spiritual. There are a large number of magic enabling skills as the Mythus game is a high magic setting. This means even a traditional fighter character can easily have some small spellcasting ability.
Dangerous Journeys has a very strong class (upper class, middle class etc) ruleset that limits the profession choice of the character and where and how they can mix in society.
The Dangerous Journeys rules are all over the place, you may need to look in two or three parts of the book to sort out how to do a particular thing. It has lots and lots of rules.
In Dangerous Journeys combat is done in 3 second Critical Turns (CT) and requires initiative to be rolled every CT. This makes for combats that take little game time but lots of real time. The combat rules can be quite deadly as well.
Spellcasting uses a points based system with various ways to generate Heka (magic). The Mythus Magic book has a lot of spells and heaps of rules on how to run a high magic campaign.
From your description of how you run your games, I think you could find a lot to like about Dangerous Journeys if you are happy to ignore a lot of the rules and just use the material you like. After a few months of playing Dangerous Journeys my players and I have decided to keep the setting material and character concepts and change our game across to the new Rolemaster Beta because we have found the rules in Dangerous Journeys to cumbersome to use as written. Nothing is simple in Dangerous Journeys, and the game feels unfinished due to it being bought up and shelved before it really got going.