Major form of methyl 3-hydroxy pent-2-enoate?
quick googling shows that for a very similar compound ethyl acetoacetate enol and ketoforms are in equilibrium with 10% of enol form. However, this equilibrium is influenced by solvent significantly. Actually, the percentage shows that the difference in stability between these two forms is veeery little. 

The difference may be attributed to the difference in stability of the bonds, i.e.   C=O + C-H is better then C=C + C-O + O-H. However, internal hydrogen bonding DOES exist and participates in stability of enol form. For example, for hexan-1,3-one, the percentage of enol form is much lower.