This is a copy of a forum post I made on our Band of Fathers clan forum, it might be useful for (new) players looking to purchase a premium tank.
This is based on data from www.wotdb.info. It shows the credit and XP multiplier for some popular premiums and approximate guesses for those where the info is not available. Please note that although 1.05 might not seem a lot, most regular tanks have a credit multiplier BELOW 1, so I added a comparison to the tanks that these premiums are close to where the info was available (tier/size). I also added a bit of opinion as I own quite a number of them:
Russian:
Churchill 1500 gold - Credits 1.15, XP 1.38 --> the Churchill is a great buy at 1500 gold and even better when on offer for 750. It is a fun tank to play and is ideally suited to grinding XP (And training Russian heavy crews!). Compared to the KV1: C 1.0, X 0.99
Matilda 1500 gold - Credits 1.11, XP 1.05 --> The Matilda is a lot like the Churchill but doesn't earn anywhere near as much, reasonable fun and useful for training USSR medium crews, but only for the die-hards. Compared to the KV1: C 1.0, X 0.99. Compared to the T-34 (Very different tank!): C 1.0, X 1.0
KV-5 7500 gold (out of shop now) - Credits ?, XP ? --> WotDB doesn't provide data for this tank, annoying because I reckon the XP multiplier is close to that of the Churchill and the Credit miltiplier is somewhere between 1.25 and 1.50. I love this tank, others hate it, my main credit farmer by far! Compared to the IS3 C .69, X 1 (KV4 would be fairer, but no data on that, might be bit better)
IS6 11000 gold - Credits ?. XP ? --> again, no info. I haven't got it, but I believe it to be similar to the KV-5 for earning potential. However, the gun isn't as good (lower DPM) and it gets some poor reviews. Compared to the IS3 C .69, X 1
German:
Lowe 12500 gold- credits ?, XP? --> staplefood for credit hungry players, no data but I believe this has one of the highest credit multipliers in game, coupled with a gun that is bound to do a lot of damage and this is a great earner. Compared to the King Tiger C .72, X 1
Dicker Max 3200 gold - Credits ?, XP ? --> Again, no data, from experience I'd say it has a low advantage on credits (1.05?) and negligible advantage on XP. It is a fun tank to play though and if you are training German crews for TDs this is a good choice. Compared to the JagdPanzer IV - C .88, X 1.
Jagdtiger 8,8 10000 gold -Credits ?, XP ? --> Don't have one, but as I understand this tank has a good earning potential, on a par with the Lowe and T-34 or just below. If you are purely after training crews the Dicker Max is probably the better (and certainly cheaper!) choice. Compared to the JagdTiger - C .68, XP 1
T25 1500 gold - Credits ?, XP ? --> I had one of these and although I sold it, it is a decent tank. It has a similar problem as the Ram II in that it meets quite a lot of tier 7s which are pretty much invulnerable to it. It makes decent credits (I suspect a 1.1 multiplier) and is useful as a German Medium crew trainer.
USA:
Ram II 1500 gold - Credits 1.2, XP 1.05 --> Had one and sold it, this tank suffers from tier drag, it is not powerful enough to fight tanks it meets frequently. It makes decent credits but for this price the
Churchill is the better choice due to better MM. Is a good crew trainer for Yankee tanks though. Compared to the M4 Sherman - C 1.1, X 1 (M4 is really a good credit maker non premium!)
T14 1500 gold -Credits 1.11, XP 1.05 --> A fun tank to play, effectively the US Matilda except it has been classified as a heavy, making it a good tank for training US crews, don't expect miracles from the earning though! Compared to T1 HT - C .9, X 1
Super Pershing 7200 gold - Credits ?, XP ?. A medium that is a heavy, opposite of T14! I played it on the test server and the lack of speed AND penetration means you can't use the gun well, this tank has awesome armour, but taking shots for the team doesn't give you credits... cheapest tier 8 and I'm sure there are people out there that like it, at least one? Likely candidate for a buff as it is one of the most complained about premiums! Compared to Pershing - C .69, X 1
T34 12000 Gold - Credits ?, XP ? - A very popular earner, on par with the Lowe, apparently hitting over 100K credits per match is quite common. Basically a turreted TD in a heavy tank package. Compared to T32 - C .8 X 1
China:
Type 62 Gift shop only - appr. 20€ - credits ?, XP ? A blast to play, you can really have some great games in this, unfortunately you can also die within 1 minute. Credit earning isn't great, similar to Dicker Max, the only other tier 6 premium. I have the impression the (non transferable...) the crew is training quite fast, so XP multiplier might be reasonable.
Type 59 7500 gold (gift shop only now?)- credits ? - XP ? - also a blast to play and a great earner on top of it. I suspect a 1.3 credit multiplier and a decent XP multiplier. This tank is worth the gold even if it has been nerfed a lot in recent patches.
France:
France is lacking in premium tanks, as far as I can tell you are doing best avoiding them. By request:
105 LeFH18B2 750 gold. Credits ?, XP ? I don't own one, but as the TD I think these are only useful for training crews for French tanks.
FCM Pak40 850 gold. Credits ?, XP? I don't own one, or played one, but as with the SPG I think these are only useful for training crews for French tanks.
Non premium Credit earners - keep these if you can!
M4 Sherman: 1.1 multiplier AND a nice tank to play (once you get used to it)
T49: Unknown multiplier but I heard good things about its earning potential, I guess it is similar to the 1.1 of the M4.
KV1: Multiplier .99 but very favourable MM means you are usually top dog which helps in the amount of damage you can do.
SU85: I don't know how it is since the nerf of the gun, but it has a x1 multiplier and used to do a lot of damage.
PzIII/IV: Multiplier of 1.08 and a fun tank to play
PzIV: .99 multiplier but with the top gun it is a real damage dealer, unfortunately it will lose that gun, unless they tweak the multiplier you are better off with the III/IV after the patch.
Hummel: 1.08 multiplier, if you like your arties, the Hummel is the best for making money.
StugIII: unknown multiplier but alleged to be really high. Looks like the German tier 5 is where it is at!
Final Thought: The top in-game tanks (Tier 8-10) and a lot of others outside tier 5/6 are almost exclusively on .68 to .7 multipliers. This should give you an idea how good a 1.3 multiplier is, that is nearly twice as good!
Edit: Fixed the red!