Taste...what makes the most difference?

So as a noob in this I'm wondering if there are one or two ingredients in beer that really make a difference in the end product. I would be tempted to say Hops and Grain, and the amount of those ingredients used. How much does the type of yeast used really matter? Or...what's really the difference between Marris Otter/Vienna, Two-Row/ Six-Row, etc.?

Every ingredient, water, grain, hops, yeast, plus process affect the end product. Never underestimate any element. A perfect recipe with poor sanitation and process will turn out bad. Using the wrong yeast, or the right yeast at wrong temperatures will make a big difference in the end product.

Marris otter is a pale british base malt. Vienna malt is continental malt that is kilned at a slightly higher temp to create a slightly darker color and toasted flavors.

2-row barley has a higher starch/husk ratio and is relatively low in protein and enzymes. The result is an easy to mash malt with higher gravity contribution per pound.

6-row barley has relatively more proteins and enzymes. It is great when mashing with non-barley grain adjuncts that are low in enzymes. Because it has more protein, it usually requires a protein rest in the mash to improve clarity in the final beer.

quite an open ended question.

honestly, EVERY aspect affects the flavor. You cannot brew a Kolsch without kolsch yeast, no matter how you try to tweak the other ingredients.

By and large, your grainbill, hop choices, and hop quantites are your primary flavor sources.

The answers to your different grain questions... start here: http://hbd.org/brewery/library/Malt101.html

i'd say the yeast is the most important part, but that's only for certain beers. Some brews use a yeast which gives a nice clean flavor and then most of your character comes from the malts and hops.

Marris Otter is a little more bready (is that the right description?) and malty then American 2-row, which is very clean. Vienna is lightly kilned so it will give a wonderful malt flavor...so will Munich. These are all technically base malts, although munich and vienna wont convert much more than themselves because of the kilning.

For certain beers, such as wheats and a lot of belgians, 99% of the character comes from the yeast. at least the fruity, estery characters

damn, we're all so quick today

isn't it amazing that you can get so many different flavors from the same basic ingedients?

malted barley
water
hops
yeast

make an infinate different set of beers...

I agree that allthe ingredients AND the process matter.

After eight months as a n00b ale brewer I finally bit the bullet and made a batch with the AnchorSteam lager yeast and my temperature controller.

Yeast matters too, ity just takes longer to developthe palate for it.

I would say first, get you water and process consistent.

When you can make consistent beer with good quality water, then start playng with hops.

When you have a consistent process with good quality water and a grip on hops, start playing with grains.

After that, yeast.