A number of track teams have tested the Bambino, the Evade, and the Casco Warp in wind tunnels. Assuming an indoor track so no issues with crosswind wind velocity vectors, the full-on pointy-tailed helmets tended to underperform the rest, mostly because in the power events you're interested in, you are changing position through too much of your ride to benefit from a helmet that needs a stable position to perform well. When it comes to these three helmets, plus the Air Attack Shield and a couple others, it comes down to how you ride -- absolute speed and also how you move your head through your ride. In a standing start 500, for example, if you start with head up, arms straight, back curved, and then transition into a flat-backed low position, you are basically in two completely different positions. The Bambino works pretty well in the low position at speed but doesn't do as well in the starting phase. In a flying 200m, it depends on how you like to ride the event. Assuming a 250m track (so you don't have to do any weird maneuvers to get speed on the banking at the right time for your start), some riders launch after a lap at high speed, while others prefer to accelerate hard right into the 200 meter line. The Bambino performs better in both aspects of the 200m because you don't change position quite as much, but if your position control is loose at all, you won't benefit from it. The Evade is particularly dependent on rider head position -- if you tilt your head from side to side at all, it interferes significantly with air flow and performance drops off quickly (to less than a traditional road helmet). If you keep your head in position well with the Evade, it does better than the Bambino but not as well as the Casco at speed.
The other aspect of individual performance is absolute speed. The Casco increases in performance as your speed increases, so it may not do much if your 500m time is in the high 40s, but if it's in the mid 30s you get quite a bit of lift from it. The Evade is fairly neutral. The Bambino doesn't improve at higher speed, and is also dependent on overall body morphology -- a bulkier torso helps the performance of the Bambino while a very thin rider won't do as well with it.
You don't mention the Air Attack. While I haven't seen it compared head to head with the others in wind tunnel testing for track purposes, subjectively it's worked really well for a lot of riders and has the advantage of significantly greater comfort. It's also most tolerant of positional changes of your head.
One thing to keep in mind about track helmets is that if you fall and you have a helmet with any kind of protuberance in back, it can catch as you slide and wrench your neck and head badly, with additional complications for your shoulders and back. It's a nasty injury. This is one reason why the Casco is so popular -- it protects equally well from hits from a number of directions, and it doesn't force any twisting injuries like a lot of other helmets. I hardly ever recommend a full-tail aero helmet any longer, and then only for endurance events and for riders who really know how to use them. Having ridden all of them, the Evade feels moderately lighter but I'm sure doesn't give the crash protection that the Casco does. The Air Attack is also good in this regard. I've seen a couple crashes in Bambinos where the rider's head isn't twisted by the helmet shape but where the rider's head definitely doesn't get to maintain a neutral position -- the helmet forces the neck into an angle which increases injury risk.
Bottom line, for your events I'd go with the Casco Warp. I watched a dozen riders using Bambinos last summer and noticed that they were almost all having trouble with keeping head position. The Evade doesn't do anything that the others don't -- at least for track. If you don't like the warmth of the Casco, or if you don't fit it well, I'd go to the Air Attack Shield. Frankly, unless you are already winning and close to record times for your age group, the helmet won't make the difference. I'd save the money or I'd recognize that physiology is more important than equipment at less than record speeds. To race those events at winning speeds, I'd put the money into motor pacing, into wheels, and simply into racing.