I think anyone looking at their first jet job from a GA background - & who doesn't think they would benefit from an hour or two in a full flight sim - would need to be supremely confident in their stick-&-rudder skills. Coming from a regional airline background would certainly help.
Whilst it's true that the same basic laws apply to all aircraft (irrespective of size or power plant), going from a light single or twin to a B737/A320 is still a huge leap, & not just in the context of systems either. Sort of like jumping out of a Hyundai & into a Ferrari 599. With regard to someone coming from a regional turbo-prop, again it would be a big help, nevertheless there are still significant differences between handling props vs jets. Not that a sim ride is about systems anyway, but different body angles for a given flightpath & responses to thrust inputs are all things that can throw a candidate off balance if not prepared.
I am not affiliated with any flight sim/flight training organisation, so this is not a sales pitch. That said, the decision on whether or not to purchase sim time is an individual one based on levels of confidence & ability as mentioned earlier, but I have to agree with Centaurus' remarks; the Flight Experience "simulator" is a pretty good rendition of an actual 737NG flight deck layout, but does not even remotely come close to the flying qualities of the real aeroplane. And whilst the genuine B737 full flight sim is also somewhat lacking, it's a hell of a lot closer to the real aeroplane than the other one - & therefore a much better investment for your interview prep (if you can afford it).
...Just another 50 cents' worth from someone who has flown all three.