Hey guys,
first post here

Thank you all for this thread, convinced me to check the bass out (and to buy one).
I went to my local music store yesterday and was happy to see that they stock nearly all the versions of the Dimension bass, so naturally, I played most of them.
I had the Squier 4 Maple, Squier 5 Maple, Squier 5 Rosewood, Am DLX 4 H Maple, Am DLX 5 H Maple. The also had the passive American one and the Mexican one but I didn't really play those. Those ugly tuners on the MIM... why would anyone do such a terrible, terrible thing?
Anyway, here are my impressions:
The main difference between the American basses and the Squiers is, hands down, the neck. It is much better on the American model. That is not to say that the neck on the Squier is bad, I just think the oil finish/asymmetric profile makes for one killer neck. It's definitely not just the truss rod and graphite rods, it also feels noticeably better.
Soundwise, I was a bit surprised. You can tell a difference but it's not easy to pick a winner. The American model did sound a bit clearer, bit more refined, a tad less boomy. I played alternating octaves on the B and A string (the intro to Everlong, to be exact...) and the string separation was better on the American model. Overtones and flageolets also sound clearer.
However, the Squiers did have much more "growl" to them. Though the B string was great on the American model, it did sound even "mightier" on the Squier.
One thing that both have in common is that the electronics cavity doesn't seem to be particularly well shielded. I had my phone in my pocket and did get some of those annoying beeps with both the Squiers and the American models.
I also a:b'ed the rosewood v the maple on the Squiers. Maple was a clear winner for me. Playing the Everlong intro again, I could tell that the string separation was much better with the maple board. The growl from the serial wiring just is a bit better controller overall (and also the red bit of the sunburst finish looks quite ugly in the flesh).
I will definitely get the black maple 5er once I have some stuff sold off, it really is a no-brainer.
However, my local store is selling the Am DLX 5H for 1150€. That is just a bargain... For anyone who has got a bit more cash to spend, i'd recommend keeping your eyes open for those kinds of deals. That neck...