In case you've been following the Sohn Conference today, billionaire investor Jeff Gundlach just went on stage and said that investors should buy the SPDR S&P Oil and Gas Exploration and Production ETF (XOP).XOP has done very well during the month of April, coinciding with the rise in oil prices. The price of WTI is up around 10% in 2018 and has pushed oil ETFs to strong gains following the correction earlier this year. I made a buy recommendation at the beginning of the year for the VanEck Vectors Oil Services ETF (OIH) to ETF Focus subscribers. XOP and OIH have high correlations although have no overlap since they operate in different spaces. My belief in recommending OIH to my subscribers was based on the upward trajectory of oil prices, and Gundlach's statement today is another bullish recommendation for the energy sector.What do you think? Are you bullish on oil and the energy sector? Are you buying individual stocks or ETFs?