I would agree with Kevin it depends on the type of play. As your looking at the A5 or the Delta Elite it's fair to say your wanting a Milsim kind of feel to the play. I started out with the BT , then added the electronic trigger and you can see where this is going. Finally switched to an Etha but to keep my Milsim side happy got the EMC add on to give me that comfortable feel but with the performance of an entry level tourney marker.I'd think carefully about what style of play you want. You'll spend a lot of money on those markers, and end up with something heavy, bulky and of low tec operation. If you ONLY ever play in large scale woods games, you'll not be too limited (apart from the hassle of lugging them around the field)
For your £250ish budget, you could buy a second hand PMR, older EGO, ETEK, Invert Mini or DM series, and fit an electronic hopper plus bottle. All will shoot faster, be more adjustable and controllable and be massively lighter and more compact than your two choices. They will be perfectly at home in woods, but also on smaller fields and airball games.
The difference is pretty phenomenal. I do love the sound of the BT on ramping as being an ex Bill Oddie the sound is quite comforting
But for performance and value for money in the long run if I know now what I did then the Etha would have been my first choice.