At 30,000 feet bombers in level flight have a very nice speed and fuel advantage, if they are well flown. I cannot think of a single World War II fighter that isn't challenged at that altitude with the exception of rocket powered and jet powered fighters (and they have limitations, as well).
I wrote a very long and detailed dissertation to answer your question and realized after I had written it that I had not answered your question.
So, here it is...short and sweet; it's the pilot, not the aircraft!
If you did not read the Map and DarBars correctly, if you did not anticipate the altitude of the bombers, if you did not factor in the climb rate of your aircraft, if you did not factor in fuel burn, and if you did not set an intercept course that would put you 3-5 k above the bombers and match their speed, then no aircraft will be "best"; you must visualize and set up the shot long before it happens.
Now, as to what aircraft you fly to accomplish this...that's up to you. Personally, I like the F4U Series, and I've shot down many buffs at 25-30 K in a Corsair. You may opt to fly an ME-262, or an ME-163, or a TA-152, or an A6M...it doesn't matter as long as you know the performance of your aircraft, have the skill level to fly the aircraft at 30K altitudes, and have the patience to set up the encounter.
Another keynote...I learned that if I want to know how to shoot down bombers...it's probably a good idea to learn how to fly them and defend them.
I'll stop here. There's more, but digest this first.
<S>
...just some thoughts