Which is better esomeprazole or ranitidine?

Depends what condition you are treating. Both drugs reduce acid in the stomach. Esomeprazole is in the class of drugs called proton-pump inhibitors and ranitidine is a histamine-2 blocker.

Esomeprazole is used to treat symptoms of gastroesophageal reflux disease (GERD) and other conditions involving excessive stomach acid such as Zollinger-Ellison syndrome. Esomeprazole is also used to promote healing of erosive esophagitis (damage to your esophagus caused by stomach acid).
Esomeprazole may also be given to prevent gastric ulcer caused by infection with helicobacter pylori (H. pylori), or by the use of nonsteroidal anti-inflammatory drugs (NSAIDs).
http://www.drugs.com/mtm/esomeprazole.html

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Ranitidine is used to treat and prevent ulcers in the stomach and intestines. It also treats conditions in which the stomach produces too much acid, such as Zollinger-Ellison syndrome. Ranitidine also treats gastroesophageal reflux disease (GERD) and other conditions in which acid backs up from the stomach into the esophagus, causing heartburn.
http://www.drugs.com/mtm/ranitidine.html