Re: Question about which Doctor Who sonic screwdrivers to buy......
Perfect timing, I've just come across this thread after doing quite a bit of research on sonics after I bought a Sonic Pen+ Ten's Sonic set.
Which, BTW, the repackaged version I bought (
http://forsthaus-bischofswerda.de/blog/wp-content/uploads/sonic-screwdriver-pen-set-i9.jpg) now has a purple (possibly UV, it didn't show lemon juice on paper though) LED and a regular black ink nib, no UV ink. This makes the old packaging the only non-replica/toy Tennant Sonic that has a blue LED, so there's that for consideration. (
http://www.stupid.com/assets/images/doctor_who_sonic_pen_and_screwdriver_set_1.jpg)
Anyway, I think you'd love to take a look at this:
Sonic Screwdriver Toys
That should explain quite a few differences that you're looking for between all these toys n' replicas out there, along with the previously mentioned votesaxon07 video toy reviews.
And for interests sake, this should explain a bit on the myth of use of Sonic toys on the actual show (TL;DR- sometimes, as a stunt prop to be tossed/blown up):
The 9th and 10th Doctor?s Sonic Screwdriver (Updated). | PurpleBlancmange
And some more. I wonder if he's a member here.
It?s almost here ? Doctor Who?s 50th Anniversary. | PurpleBlancmange
And while we're talking about River Song's Sonic, before the 50th aired I was hell bent on my own conspiracy theory that since Tennant and Smith would be appearing together in the episode, that Tennant would possibly leave his sonic with Smith before he leaves for his own timeline, enabling Smith to mod it and give it to River on their last night (as posted above). It's already seen the TARDIS creates the sonic, so Tennant could have easily replaced his and still kept everything continuous and plot hole free. Alas, the episode ended up with none of that, but it was a fun speculation anyway.
Also Capaldi's apparently been posting lots of fan made posters on his Facebook page, so I've heard. If its not on any official BBC site, admire, but don't trust it haha.