If you are new to aquarium keeping, bigger tanks are easier to maintain. I would say if you want a bigger tank, have space for it and can afford it, go for it.
From personal experience, i didnt really realise how much more expensive a bigger tank is than a smaller one however.
Obviously the tank you are thinking about is free. Running costs, ie power will be nominally more expensive. The cost increase for me was in getting bigger filters, longer light fittings, more powerful heater, more substrate, more driftwood and rock work. The amount of water conditioner and ferts will go up. And of course your livestock costs will increase.
You havent said whether the tank comes with all the equipment and is it in good condition? Are you planning on running this bigger tank and keeping the 2 smaller ones?
I would recommend keeping the 70 litre as a quarantine tank in case its needed.
One thing that would benefit you would be transfering the filter media from your partially cycled 100 litre to the 130 litre. This will speed up the cycling process immensely.
All in all i would go for it, assuming you have space, that it wont stretch your finances too far, and that the 130 litre tank is in good condition.