Sierra v dismal spamcan
Hi captain echo,
Of the two aircraft, having flown both and also the Firefly (T67B), I should say that at your stage of training, and especially after previously training on the Firefly, the Technam Sierra would be much the better choice. (After the Firefly handling the Pa28 would be like stirring treacle).
The Pa28 was designed round about the early sixties and at a time when the US small aircraft industry was trying to make aeroplanes as much like cars as possible. They wanted families, that already owned a family car, to buy a family aeroplane! Hence, they designed the Pa28 to be as safe and as fool proof as possible in the hands of some ham-fisted 'daddy' figure with little training and limited flying aptitude. This resulted in an aeroplane with safe but soggy handling.
So if you want to fly a machine that looks like a post war Ford V8 Pilot (and handles like one) then the Pa28 is the way to go. (This is not to detract from its usefulness at IMC level, when you want rock-solid stability, or for taking the family for a ride on Sunday afternoon; but you aren't doing IMC or taking the family for a spin).
To 'learn your trade' I feel you need an aircraft with crisp generic handling, (such as for example the Chipmunk had) and that isn't the Pa28.
The Sierra is modern and typically Italian. Like a modern Alfa-Romeo or Fiat it handles crisply and generically and is generally a delight to fly.
As to which of the deals you have been offered is best, that depends on how many hours you expect to fly in a year.
Good luck!
BP.