Which one is the stronger Lewis base: diethyl ether or tetrahydrofuran?
Which is &quot;better&quot;? In some specific reaction, with all other circumstances identified. Ether is a little too volatile for my preferences, but THF is not bad. I like the smell of ether, but the odor of THF is OK. Little problem with oxygen (fire and peroxides) with both of them, so you must be careful with both.
The difference in enthalpy of formation (11.6 kJ/mol) is small compared with activation energies of typical organic reactions (~100 kJ/mol), so &quot;better&quot; might be related to human preferences more than than chemical performance.
A chemist might already have a feel for the molecular configurations of these molecules, but a physicist could benefit from making the models or looking at them:
 

The ability of THF to poke the BF3 molecule better than ether can is apparent. Whether this is the controlling factor in which is &quot;better&quot; remains to be seen. I'll go out on a limb and say that either one will work, although the results (convenience, yield, expense, etc.) could easily be +/- 20-50%, depending on the situation. In a lab, one might work better; in industry, the other might be preferable.
Either solvent could probably be optimized for best performance under slightly different conditions, and these optimum conditions will not be the condition you choose for the first experiment. Probably a dozen experiments will suggest which solvent could be the better choice. The literature should suggest the better (or more typical) choice for your needs.
Ref. https://en.wikipedia.org/wiki/Activation_energy