LINGO is an open source application for mathematical modeling. How about your experience about LINGO? What are the uncommon tools in LINGO to solve optimization models?
LINGO is not open source. It is a commercial software from LINDO systems. GAMS is a modeling environment for optimization problems, but itself is not a solver. It contains all popular free and open source solvers, and trial versions for others. If you have license for a commercial solver, you can use it in conjunction with GAMS. I personally prefer CPLEX, because that's what I've used for many years.