Both are very good and really, it's all down to your personal preference and/or concept.
Flame:
- Bonfire is good for keeping melee'ers off you. It creates a nice safe haven for those foes that just love to bum rush you.
- Char is a great single target hold that last long and recharges fairly quick right out of the box.
- Fire Shield is a very good shield like most APP shields for blasters. You get S/L + Fire resists, and + a little Cold resist as well.
- Melt Armor is a Def/Resist Debuff power, that is really not that great, imo for blasters because of the 200s base rech.
- Rise of the Phoenix is a really great self rez that will stun any foes nearby (incl bosses) and give you a small window of invincibility.
Force:
- Personal Force Field is a nice "Oh crap!" power to give you high def and resists, but you are not able to attack. It can allow you to run away, if the mobs don't get you during its activation time and there's no DoT. A very good power.
- Repulsion Field is a PBAoE power that can KB foes from you. It ticks too slowly and does not perform as well as Bonfire, imo. It is a toggle so it will cost you end to run it and the more you KB, the more end it costs. ( Bonfire has a higher mag KB, ticks much faster, and costs very little endurance comparatively.)
- Repulsion Bomb is a fun power but a long animation. It is a AoE Knock-down power with a 40% chance to mag 2 stun (only gets minions). It does ok damage.. not great, but ok. Again, a fun power, imo.
- Temp Invulerability is your shield power, but only S/L resists. The S/L resists are a little higher on this power because you don't get resistance to anything else like Fire or Energy (fromt eh electric shield), or etc.
- Force of Nature is an "Unstoppable" type of power that gives you high resists to everything (except psy) and +recovery for 2 mins... then you crash and lose all your endurance and cannot recover end for another 15 secs. (NO HP crash with this power--unlike the tanker version.) This is another great "oh crap!" power that actually allows you to fight while using it.
....Really good powers in both sets and each play a little differently. So again, it's really up to you and your personally preferences and/or toon concept.
One thing to add about Rise of the Phoenix... it's not just a self rez that stuns and knocks back enemies, it's a second nuke. It hits hard, stuns even bosses, knocks things flying, and it leaves you untouchable for 15 seconds while only leaving you helpless for four. That's 11 seconds of payback to a bunch of stunned and damaged enemies while invincible... plenty of time to dump some AoEs, pop Aid Self or a green pill to top off your health, and even retreat if need be.
Of course you do have to die to use it, but come on, you're a Blaster. You're gonna die from time to time, so why not grab a power that lets you make whatever killed you really sorry they did? 
Cascade, level 50 Blaster (NRG/NRG since before it was cool)
Mechmeister, level 50 Bots / Traps MM
FAR too many non-50 alts to name
[u]Arcs[u]
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THanks for replies guys, very informative 
Think i will go for fire as at least 4 of those powers i would use where as force seems more situational and only a couple of them seem attractive.
Rise of phoenix is a huge reason to go fire as I am very squishy and if theres no tank I can over agro.
My fire/energy blaster is lvl 40 now and trying to figure out which ancillary power to go for. The energy side of my blaster is only for self defense/boosts as I try to keep max range between me and mobs.
So what are the good & bad points of flame mastery & force mastery? both sound like they fit the concept of the toon.