Say I have ADHD, which will wow me and hold my interest longer? i.e. is more fun and entertaining?

That's a tough one.

Personally I prefer 2, due to the better (somewhat SW-Universe-subversive) plot, the fact you can turn a lot of your companions into Jedi, and all that. A lot of people like 2 better than 1 for these reasons; however, that's not really related to fun/entertaining (necessarily) - and if you're expecting a more "standard" Star Wars experience (clear good guys, clear bad guys, SW power game), then you need to be aware that it is most definitely subverting the Universe in ways you may not like. Then again, maybe you'll be like me (and many others) and consider this story "fresh" because of it - not to mention the interesting characters (generally damaged characters) that accompany you.

In contrast, 1 has a more "standard" SW plot - although there is a twist partway through (albeit a pretty obvious one). If you want to be a bad-ass good guy, or a bad-ass evil bastard, 1 probably has more truly "heroic" and "dastardly" deeds you can do - that is, straight up good/bad choices with not so much in the way of introspection or second-guessing. As an evil character, there are a couple of truly hilariously evil things you can do to your companions.

The first one also has more "familiar" locations than the second one - that is, more locations from the movies (albeit thousands of years before the events in the movies occurred).

Both of them have combat that on the one hand can look pretty cool, but on the other hand gets really easy really fast (to the point of tedium towards the end).

The second one does have the added disadvantage of starting off on a very linear path, which seems to go on forever - it does open up (just like the first), but it seems to take forever to get to that point. Many people really hate the first few levels of 2 (not me, but I'm weird) - whereas the first few levels of the first one tend to be more interesting and engaging, and it doesn't take as long before you have a ship and can go pretty much wherever you want.

The first one starts you off as a non-Jedi, and you only become a Jedi after the first few "levels" - whereas in the second one, you're a Jedi immediately (and then you become a souped-up Jedi when you get your "prestige class"). Which makes the first one more varied initially, while the second one has extra Jedi powers etc. that the first one lacks (also jedi stances, although there's a mod that adds them to the first as well).

Not sure if that helps at all - as it really comes down to what exactly is engaging for you personally.

I actually played the second one first, and only got the second one years later. Apart from the second one revealing some (minor) things that occurred in the first one, I don't think I spoiled myself doing this, and still played through the first one multiple times - though I still prefer the second one overall.

The first one, even though it's a very standard Star Wars story. I didn't like the second one because it's not very respectful of the meta-lore of the series (and I got the impression that there was an attempt to be edgy, in the wrong way).

Still, if you are going to pick the second game, do know that it's incomplete and with many bugs. There are essential mods that fix those issues though.

That is completely subjective: what I find fun you might find dreadfully tedious.

The second engine has a lot more depth, since Obsidian improved on the basic experience of BioWare's original (and the plethora of irritating bugs have been fixed if you install the missing content, which is highly recommended, since Obsidian did not finish the game before the scheduled Christmas release, so the vanilla game is almost totally broken) but it also has some fairly unsatisfying elements. (For instance, about half-way through your large team breaks into two maniples; also in the finale you must choose another character to aid you, so you play a lot of the game not as your chosen character.)

Similarly, the first game starts with your character without Jedi powers. (A Jedi is a D&D cleric. There are no magic users in the Star Wars skin of the engine.) It is possible to reach half the game's level cap before the transition. A lot of people (me included) avoid levelling their character until the transition in order to have more Jedi levels (hence Jedi-specific feats and powers). The finale of the first game eventually becomes a high-noon shoot-out, and the companions you bring are ignored.

The first game has a romance. The second gives lip-service to a romance, but if you blink you will miss it.

The first game has a real-time turret shooting mini-game that is very difficult, and no difficulty adjustment (unlike the sequel) but there is a mod to fix this.

I am currently playing both again, simultaneously. There are some very tedious bits and some excellent conversations and set-action pieces. (The combat is generally much better in the sequel.)

HTH

And/or Paladin.

Sim. :)

Also, my comment about the combat being better in the sequel requires a large caveat, since the AI is atrocious. (There is a mod to fix it, however. The community is vast and dedicated, which is a big plus for any purchase of either game.) In any challenging (boss-) fight you will need to micromanage your party (of three characters), but —— more importantly —— you must disengage from the fight at the start, lest the characters default to their script attack (which is to charge into mêlée for the default aggressive mode, selected by the rightmost of the left scroll-boxes at the bottom edge of the screen). This is despite clearing the command stack and creating a new list of actions. Quite often the AI will determine to attack, despite the disengage instruction, too.

That said, one can select stationary to prevent this (or ranged for firearms-wielding characters).

Playing them simultaneously is quite fun, despite the simplistic engine of the first game and the flaws of the second. (I still get clipping issues ALL THE TIME, particularly after activating the jedi speed power. Often the only way to escape is to select another character and move them. Sometimes I have had to select the third character, since the first two were both immobile due to this clipping error. I don't remember having this issue with the vanilla game so it may be due to all the mods I have added.)