Originally Answered: Two intense 30 minute workouts a week in Gym vs. Light in-home 15 minute workout 6 nights a week?
I say it is time to give up your gym membership and do workouts in your home or outdoors if the weather is nice. Focus on bodyweight training to help you achieve the desired physique, health, and body image you are striving for. Especially if you are doing high intensity interval training with your bodyweight alone, you will burn more calories and work harder than going to the gym to use cardio machines or lift weights. The science behind bodyweight training is that you work many more muscles while doing a single bodyweight exercise simultaneously. When more muscles are worked, the more calories you will burn. Say for instance a pushup, yes you are working the shoulders, chest, back, and triceps, but you are also working the core and leg muscles to keep you stablized from falling. The traditional bench press on the other hand does not work that many muscles so you would be doing yourself a disservice with the bench press exercise yet you will see many guys focusing on their bench press max since they don't know any better unfortunately.
I'm sure if you do your research you can find a library of bodyweight exercises that can be done along with their variations whether you want to make them easier or harder. You have a couple of options for workout ideas that I'll give to you off the top of my head. If you don't know what any of them are, google search them and you will find the answer. You could do bodyweight circuit training, mixing up different exercises and turning them into a circuit for however many rounds you feel you may be able to go. For example, I could do 3 minute rounds, 1 minute pushups, 1 minute mountain climbers, 1 minute jump squats, take a 1 minute break, then go on to the second round. TABATA is another great option and excellent if you are extremely short on time but still want to fit in a workout. 4 minutes total, 20 seconds of work followed by 10 seconds of rest and repeat until the 4 minutes are up. If you felt it was too short, you could always do more and perhaps choosing a different bodyweight exercise for your second round. If the weather seems pleasing for you, do some running workouts (instead of using a treadmill @ the gym) or do jumping rope exercises to get the cardio in while burning fat. If you have stairs in your home or there are some outside nearby your home, add stair workouts in. This is excellent for leg muscle stamina while expending countless calories. Instead of light in-home workouts, complete them at a much higher intensity instead. Research shows that higher intensity workouts (HIIT) is more beneficial for getting lean and toned because you will work harder in a shorter amount of time (usually no longer than 30 minutes) causing you to lose calories at a more rapid pace than if you were to use cardio machines or lift weights at the gym. On top of that, you will become more of a highly conditioned athlete ready to function at your best both during physical training and doing everyday chores. High intensity bodyweight training is perfect because you do not need a full hour to workout, a good choice I'd say if you don't have all the time in the world for exercise, which most people don't.
The pros heavily outweight the cons for in-home bodyweight training. You save time and money by not having to spend money each month on gym membership, not having to wait for someone to finish a cardio machine or weight station anymore, not having to drive to and from the gym, not having to spend extra money on gasoline for driving to and from the gym, and the list goes on. Ultimately, when you learn that your body is your gym, you feel independent knowing that you no longer depend on a gym to get in shape. As long as you have enough space to do a proper push up, your training can be done anywhere in the world under any circumstances. Since you would be doing high intensity interval training, it's best to start training 3 days a week as a minimum. If you feel your body can tolerate more later on, you can increase to 4-6 days a week (although 6 days a week may not be necessary since the purpose of HIIT is for you to not have to workout that many days of the week). The key is to stay consistent. You don't have to workout everyday or almost everyday but you do need to workout at least bare minimum 2-3 times a week to maintain a healthful state or see some progression. It's better to do this than to workout 6 days for one week and only workout one day the following week. Keep a steady rate of training days each week, it should not be a constant roller coaster.
As your job is very sedentary, I suggest to you at least every hour to get up and walk around for at least 5 minutes. You will be doing your body a favor. Human bodies are designed to move, not to sit for prolonged hours. There are many health benefits for following this simple rule rather than to sit without standing for too many hours. If you want to be more active yet, do some jogging in place during your work break or during your 5 minutes getting off of your chair. If the weather is nice, walk outside for however long you please. The point is to get your body moving at all costs and reduce your sedentary lifestyle as much as possible. With that said, you also really want to make sure you are focusing on proper nutrition, choosing healthful foods over processed ones. A terrible combination would be living a sedentary lifestyle while consuming high calorie unhealthy food. This is where weight gain and terrible health consequences come into play. Make sure you are conscious about that.
Hopefully I have answered your question, best of luck!