It is not black and white?
Is there a command bond? (e.g. £8k flat for two years).Do you have to pay for type rating on jet (£23k?). If so you need to gauge the market. Market going UP get jet time as FO, Market going DOWN get TP Command.
Never turn down a Command? I work with guys who regret getting TP command when all current the jobs are asking for jet time. Its a credibility thing with some operators. It is very easy to get stuck, especially if the TP is small, domestic only etc. Don't listen to these guys who say that there is a golden rule. Be prepared to step outside the SOPs when the situation demands.
It takes courage to walk away from an offer of Command when it will result in a career cul de sac. Keep as much flexibility as you can and get on a universal type (whether heavy TP or Jet) such as A320/737/EMB145/ATR/Dash8 - that will give you mobility. The important thing is to keep working during the downturn!
I wish Id taken my own advice !!!